diff --git a/.travis.yml b/.travis.yml
index 607c72b520..981e8727f8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,17 +4,31 @@
 # There's a docker image pupillabs/pupil-docker-ubuntu:latest which contains all
 # required dependencies for the test-suite to run.
 
-os: minimal
-services: docker
+jobs:
+  include:
+    - name: pytest
+      os: minimal
+      services: docker
+      before_install:
+        - docker pull pupillabs/pupil-docker-ubuntu:latest
+        - chmod +x ./.travis/*.sh
+      script:
+        - >
+          docker run --rm
+          -v `pwd`:/repo
+          -w /repo
+          pupillabs/pupil-docker-ubuntu:latest
+          /bin/bash /repo/.travis/run_tests.sh
 
-before_install:
-  - docker pull pupillabs/pupil-docker-ubuntu:latest
-  - chmod +x ./.travis/*.sh
-
-script:
-  - >
-    docker run --rm
-    -v `pwd`:/repo
-    -w /repo
-    pupillabs/pupil-docker-ubuntu:latest
-    /bin/bash /repo/.travis/run_tests.sh
+    - name: black formatting check
+      language: python
+      before_script:
+        - pip install -U pip
+        - pip install black
+      script:
+        - >
+          black . --check --exclude pupil_src/tests || (
+            echo -e "\033[0;31m PLEASE RUN THE BLACK FORMATTER ON YOUR CODE: \033[0m" &&
+            echo "See https://github.com/psf/black for details" &&
+            false
+          )
diff --git a/pupil_src/launchables/service.py b/pupil_src/launchables/service.py
index 81cc2ed77b..6666c21c51 100644
--- a/pupil_src/launchables/service.py
+++ b/pupil_src/launchables/service.py
@@ -193,7 +193,6 @@ def get_dt():
             "min_calibration_confidence", 0.8
         )
 
-
         audio.set_audio_mode(
             session_settings.get("audio_mode", audio.get_default_audio_mode())
         )
@@ -226,7 +225,12 @@ def get_dt():
         def handle_notifications(n):
             subject = n["subject"]
             if subject == "start_plugin":
-                g_pool.plugins.add(plugin_by_name[n["name"]], args=n.get("args", {}))
+                try:
+                    g_pool.plugins.add(
+                        plugin_by_name[n["name"]], args=n.get("args", {})
+                    )
+                except KeyError as err:
+                    logger.error(f"Attempt to load unknown plugin: {err}")
             elif subject == "service_process.should_stop":
                 g_pool.service_should_run = False
             elif subject.startswith("meta.should_doc"):
@@ -272,7 +276,6 @@ def handle_notifications(n):
                         gaze_pub.send(gaze_datum)
                         events["gaze"].append(gaze_datum)
 
-
                 for plugin in g_pool.plugins:
                     plugin.recent_events(events=events)
 
diff --git a/pupil_src/shared_modules/accuracy_visualizer.py b/pupil_src/shared_modules/accuracy_visualizer.py
index 2c6015f810..e1f305119a 100644
--- a/pupil_src/shared_modules/accuracy_visualizer.py
+++ b/pupil_src/shared_modules/accuracy_visualizer.py
@@ -26,7 +26,7 @@
 )
 from plugin import Plugin
 
-from gaze_mapping import registered_gazer_classes_by_class_name
+from gaze_mapping import gazer_classes_by_class_name, registered_gazer_classes
 from gaze_mapping.notifications import (
     CalibrationSetupNotification,
     CalibrationResultNotification,
@@ -80,7 +80,9 @@ def clear(self):
         self.__gazer_class = None
         self.__gazer_params = None
 
-    def update(self, gazer_class_name: str, gazer_params=..., pupil_list=..., ref_list=...):
+    def update(
+        self, gazer_class_name: str, gazer_params=..., pupil_list=..., ref_list=...
+    ):
         if (
             self.gazer_class_name is not None
             and self.gazer_class_name != gazer_class_name
@@ -107,7 +109,7 @@ def __gazer_class_from_name(gazer_class_name: str) -> T.Optional[T.Any]:
             logger.info("Accuracy visualization is disabled for HMD calibration")
             return None
 
-        gazers_by_name = registered_gazer_classes_by_class_name()
+        gazers_by_name = gazer_classes_by_class_name(registered_gazer_classes())
 
         try:
             gazer_cls = gazers_by_name[gazer_class_name]
diff --git a/pupil_src/shared_modules/calibration_choreography/base_plugin.py b/pupil_src/shared_modules/calibration_choreography/base_plugin.py
index 82654d0498..b43f183a97 100644
--- a/pupil_src/shared_modules/calibration_choreography/base_plugin.py
+++ b/pupil_src/shared_modules/calibration_choreography/base_plugin.py
@@ -315,8 +315,8 @@ def on_choreography_successfull(
             calib_data = {"ref_list": ref_list, "pupil_list": pupil_list}
             self._start_plugin(self.selected_gazer_class, calib_data=calib_data)
         elif mode == ChoreographyMode.VALIDATION:
+            assert self.g_pool.active_gaze_mapping_plugin is not None
             gazer_class = self.g_pool.active_gaze_mapping_plugin.__class__
-            assert gazer_class == self.selected_gazer_class
             gazer_params = self.g_pool.active_gaze_mapping_plugin.get_params()
 
             self._start_plugin("Accuracy_Visualizer")
@@ -448,8 +448,7 @@ def update_ui(self):
         )
         if self.shows_action_buttons:
             self.__ui_button_validation.read_only = (
-                self.selected_gazer_class
-                is not self.g_pool.active_gaze_mapping_plugin.__class__
+                self.g_pool.active_gaze_mapping_plugin is None
             )
 
     def deinit_ui(self):
diff --git a/pupil_src/shared_modules/calibration_choreography/screen_marker_plugin.py b/pupil_src/shared_modules/calibration_choreography/screen_marker_plugin.py
index 330e709ae8..c59b12e163 100644
--- a/pupil_src/shared_modules/calibration_choreography/screen_marker_plugin.py
+++ b/pupil_src/shared_modules/calibration_choreography/screen_marker_plugin.py
@@ -67,6 +67,14 @@ def selection_label(cls) -> str:
     def selection_order(cls) -> float:
         return 1.0
 
+    @staticmethod
+    def get_list_of_markers_to_show(mode: ChoreographyMode) -> list:
+        if ChoreographyMode.CALIBRATION == mode:
+            return [(0.5, 0.5), (0.0, 1.0), (1.0, 1.0), (1.0, 0.0), (0.0, 0.0)]
+        if ChoreographyMode.VALIDATION == mode:
+            return [(0.5, 1.0), (1.0, 0.5), (0.5, 0.0), (0.0, 0.5)]
+        raise ValueError(f"Unknown mode {mode}")
+
     def __init__(
         self,
         g_pool,
@@ -269,7 +277,7 @@ def _perform_start(self):
             )
             return
 
-        self.__current_list_of_markers_to_show = self.__get_list_of_markers_to_show(
+        self.__current_list_of_markers_to_show = self.get_list_of_markers_to_show(
             mode=self.current_mode,
         )
         self.__currently_shown_marker_position = None
@@ -289,14 +297,6 @@ def _perform_stop(self):
 
     ### Private
 
-    @staticmethod
-    def __get_list_of_markers_to_show(mode: ChoreographyMode,) -> list:
-        if ChoreographyMode.CALIBRATION == mode:
-            return [(0.5, 0.5), (0.0, 1.0), (1.0, 1.0), (1.0, 0.0), (0.0, 0.0)]
-        if ChoreographyMode.VALIDATION == mode:
-            return [(0.5, 1.0), (1.0, 0.5), (0.5, 0.0), (0.0, 0.5)]
-        raise ValueError(f"Unknown mode {mode}")
-
     def _on_window_did_close(self):
         self._signal_should_stop(mode=self.current_mode)
 
diff --git a/pupil_src/shared_modules/csv_utils.py b/pupil_src/shared_modules/csv_utils.py
index cbd888896b..b80a803edb 100644
--- a/pupil_src/shared_modules/csv_utils.py
+++ b/pupil_src/shared_modules/csv_utils.py
@@ -14,15 +14,16 @@
 import typing as t
 
 
-CSV_EXPORT_RAW_TYPE = t.TypeVar('CSV_EXPORT_RAW_TYPE')
+CSV_EXPORT_RAW_TYPE = t.TypeVar("CSV_EXPORT_RAW_TYPE")
 CSV_EXPORT_LABEL_TYPE = t.AnyStr
 CSV_EXPORT_VALUE_TYPE = t.Any
 CSV_EXPORT_VALUE_GETTER_TYPE = t.Callable[[CSV_EXPORT_RAW_TYPE], CSV_EXPORT_VALUE_TYPE]
-CSV_EXPORT_SCHEMA_TYPE = t.List[t.Tuple[CSV_EXPORT_LABEL_TYPE, CSV_EXPORT_VALUE_GETTER_TYPE]]
+CSV_EXPORT_SCHEMA_TYPE = t.List[
+    t.Tuple[CSV_EXPORT_LABEL_TYPE, CSV_EXPORT_VALUE_GETTER_TYPE]
+]
 
 
 class CSV_Exporter(abc.ABC, t.Generic[CSV_EXPORT_RAW_TYPE]):
-
     @classmethod
     @abc.abstractmethod
     def csv_export_schema(cls) -> CSV_EXPORT_SCHEMA_TYPE:
@@ -33,10 +34,17 @@ def csv_export_labels(cls) -> t.Iterable[CSV_EXPORT_LABEL_TYPE]:
         return tuple(label for label, _ in cls.csv_export_schema())
 
     @classmethod
-    def csv_export_values(cls, raw_value: CSV_EXPORT_RAW_TYPE) -> t.Iterable[CSV_EXPORT_VALUE_TYPE]:
+    def csv_export_values(
+        cls, raw_value: CSV_EXPORT_RAW_TYPE
+    ) -> t.Iterable[CSV_EXPORT_VALUE_TYPE]:
         return tuple(getter(raw_value) for _, getter in cls.csv_export_schema())
 
-    def csv_export(self, raw_values: t.Iterable[CSV_EXPORT_RAW_TYPE], export_dir: str, export_name: str) -> str:
+    def csv_export(
+        self,
+        raw_values: t.Iterable[CSV_EXPORT_RAW_TYPE],
+        export_dir: str,
+        export_name: str,
+    ) -> str:
 
         export_path = os.path.abspath(os.path.join(export_dir, export_name))
 
@@ -63,7 +71,9 @@ def read_key_value_file(csvfile):
     if "key" not in first_line or "value" not in first_line:
         csvfile.seek(0)  # Seek to start if first_line is not an header
     dialect = csv.Sniffer().sniff(first_line, delimiters=",\t")
-    reader = csv.reader(csvfile, dialect, quoting=csv.QUOTE_NONE, escapechar='\\')  # create reader
+    reader = csv.reader(
+        csvfile, dialect, quoting=csv.QUOTE_NONE, escapechar="\\"
+    )  # create reader
     for row in reader:
         kvstore[row[0]] = row[1]
     return kvstore
@@ -80,7 +90,7 @@ def write_key_value_file(csvfile, dictionary, append=False):
     Returns:
         None: No return
     """
-    writer = csv.writer(csvfile, delimiter=",", quoting=csv.QUOTE_NONE, escapechar='\\')
+    writer = csv.writer(csvfile, delimiter=",", quoting=csv.QUOTE_NONE, escapechar="\\")
     if not append:
         writer.writerow(["key", "value"])
     for key, val in dictionary.items():
diff --git a/pupil_src/shared_modules/file_methods.py b/pupil_src/shared_modules/file_methods.py
index e5b41c1399..c916ec7060 100644
--- a/pupil_src/shared_modules/file_methods.py
+++ b/pupil_src/shared_modules/file_methods.py
@@ -353,17 +353,13 @@ def _deep_copy_serialized_dict(self):
         return Serialized_Dict(python_dict=dict_copy)
 
     def _deep_copy_dict(self):
-
         def unpacking_ext_hook(self, code, data):
             if code == self.MSGPACK_EXT_CODE:
                 return type(self)(msgpack_bytes=data)._deep_copy_dict()
             return msgpack.ExtType(code, data)
 
         return msgpack.unpackb(
-            self._ser_data,
-            raw=False,
-            use_list=False,
-            ext_hook=unpacking_ext_hook,
+            self._ser_data, raw=False, use_list=False, ext_hook=unpacking_ext_hook,
         )
 
 
diff --git a/pupil_src/shared_modules/gaze_mapping/__init__.py b/pupil_src/shared_modules/gaze_mapping/__init__.py
index 5043b2f2f8..e9926e7587 100644
--- a/pupil_src/shared_modules/gaze_mapping/__init__.py
+++ b/pupil_src/shared_modules/gaze_mapping/__init__.py
@@ -19,12 +19,18 @@ def registered_gazer_classes() -> list:
     return gazer_base.GazerBase.registered_gazer_classes()
 
 
-def registered_gazer_labels_by_class_names() -> dict:
-    return {cls.__name__: cls.label for cls in registered_gazer_classes()}
+def user_selectable_gazer_classes() -> list:
+    gazers = registered_gazer_classes()
+    gazers = filter(lambda g: g is not GazerHMD3D, gazers)
+    return list(gazers)
 
 
-def registered_gazer_classes_by_class_name() -> dict:
-    return {cls.__name__: cls for cls in registered_gazer_classes()}
+def gazer_labels_by_class_names(gazers: list) -> dict:
+    return {cls.__name__: cls.label for cls in gazers}
+
+
+def gazer_classes_by_class_name(gazers: list) -> dict:
+    return {cls.__name__: cls for cls in gazers}
 
 
 default_gazer_class = Gazer3D
diff --git a/pupil_src/shared_modules/gaze_mapping/gazer_3d/gazer_hmd.py b/pupil_src/shared_modules/gaze_mapping/gazer_3d/gazer_hmd.py
index f232bcc956..bd02e730b9 100644
--- a/pupil_src/shared_modules/gaze_mapping/gazer_3d/gazer_hmd.py
+++ b/pupil_src/shared_modules/gaze_mapping/gazer_3d/gazer_hmd.py
@@ -23,6 +23,7 @@
 from gaze_mapping.gazer_base import (
     GazerBase,
     Model,
+    CalibrationError,
     NotEnoughDataError,
     FitDidNotConvergeError,
 )
@@ -46,6 +47,13 @@
 logger = logging.getLogger(__name__)
 
 
+class MissingEyeTranslationsError(CalibrationError):
+    message = (
+        "GazerHMD3D can only be calibrated if it is "
+        "initialised with valid eye translations."
+    )
+
+
 class ModelHMD3D_Binocular(Model3D_Binocular):
     def __init__(self, *, intrinsics, eye_translations):
         self.intrinsics = intrinsics
@@ -53,6 +61,8 @@ def __init__(self, *, intrinsics, eye_translations):
         self._is_fitted = False
 
     def _fit(self, X, Y):
+        if self.eye_translations is None:
+            raise MissingEyeTranslationsError()
         assert X.shape[1] == _BINOCULAR_FEATURE_COUNT, X
         unprojected_ref_points = Y
 
@@ -109,7 +119,7 @@ class GazerHMD3D(Gazer3D):
     def _gazer_description_text(cls) -> str:
         return "Gaze mapping built specifically for HMD-Eyes."
 
-    def __init__(self, g_pool, *, eye_translations, calib_data=None, params=None):
+    def __init__(self, g_pool, *, eye_translations=None, calib_data=None, params=None):
         self.__eye_translations = eye_translations
         super().__init__(g_pool, calib_data=calib_data, params=params)
 
diff --git a/pupil_src/shared_modules/gaze_mapping/gazer_base.py b/pupil_src/shared_modules/gaze_mapping/gazer_base.py
index a4de243589..0abca2189d 100644
--- a/pupil_src/shared_modules/gaze_mapping/gazer_base.py
+++ b/pupil_src/shared_modules/gaze_mapping/gazer_base.py
@@ -44,6 +44,14 @@ class NotEnoughDataError(CalibrationError):
     message = "Not sufficient data available."
 
 
+class NotEnoughPupilDataError(NotEnoughDataError):
+    message = "Not sufficient pupil data available."
+
+
+class NotEnoughReferenceDataError(NotEnoughDataError):
+    message = "Not sufficient reference data available."
+
+
 class FitDidNotConvergeError(CalibrationError):
     message = "Model fit did not converge."
 
@@ -194,18 +202,25 @@ def __init__(
             self._announce_calibration_setup(calib_data=calib_data)
             try:
                 self.fit_on_calib_data(calib_data)
-            except CalibrationError:
+            except CalibrationError as err:
                 if raise_calibration_error:
                     raise  # Let offline calibration handle this one!
                 logger.error("Calibration Failed!")
                 self.alive = False
-                self._announce_calibration_failure(reason=CalibrationError.__name__)
+                self._announce_calibration_failure(reason=err.message)
             except Exception as err:
                 import traceback
 
-                self._announce_calibration_failure(reason=err.__class__.__name__)
                 logger.debug(traceback.format_exc())
-                raise CalibrationError() from err
+                if raise_calibration_error:
+                    raise CalibrationError() from err  # Let offline calibration handle this one!
+                logger.error("Calibration Failed!")
+                self.alive = False
+                try:
+                    reason = err.args[0]
+                except (AttributeError, IndexError):
+                    reason = err.__class__.__name__
+                self._announce_calibration_failure(reason=reason)
             else:
                 self._announce_calibration_success()
                 self._announce_calibration_result(params=self.get_params())
@@ -214,8 +229,9 @@ def __init__(
         else:
             raise ValueError("Requires either `calib_data` or `params`")
 
-        # used by pupil_data_relay for gaze mapping
-        g_pool.active_gaze_mapping_plugin = self
+        if self.alive:
+            # Used by pupil_data_relay for gaze mapping.
+            g_pool.active_gaze_mapping_plugin = self
 
     def get_init_dict(self):
         return {"params": self.get_params()}
@@ -257,7 +273,9 @@ def fit_on_calib_data(self, calib_data):
             pupil_data, self.g_pool.min_calibration_confidence
         )
         if not pupil_data:
-            raise NotEnoughDataError
+            raise NotEnoughPupilDataError
+        if not ref_data:
+            raise NotEnoughReferenceDataError
         # match pupil to reference data (left, right, and binocular)
         matches = self.match_pupil_to_ref(pupil_data, ref_data)
         if matches.binocular[0]:
diff --git a/pupil_src/shared_modules/gaze_mapping/utils.py b/pupil_src/shared_modules/gaze_mapping/utils.py
index df8139ab34..56dbeb657c 100644
--- a/pupil_src/shared_modules/gaze_mapping/utils.py
+++ b/pupil_src/shared_modules/gaze_mapping/utils.py
@@ -32,8 +32,8 @@ def _filter_pupil_list_by_confidence(pupil_list, threshold):
 
 
 def _match_data_batch(pupil_list, ref_list):
-    assert pupil_list
-    assert ref_list
+    assert pupil_list, "No pupil data to match"
+    assert ref_list, "No reference data to match"
     pupil0 = [p for p in pupil_list if p["id"] == 0]
     pupil1 = [p for p in pupil_list if p["id"] == 1]
 
@@ -45,9 +45,9 @@ def _match_data_batch(pupil_list, ref_list):
     num_mono_right = len(matched_pupil0_data[0])
     num_mono_left = len(matched_pupil1_data[0])
 
-    logger.info(f"Collected {num_bino} binocular references.")
-    logger.info(f"Collected {num_mono_right} right eye monocular references.")
-    logger.info(f"Collected {num_mono_left} left eye monocular references.")
+    logger.debug(f"Collected {num_bino} binocular references.")
+    logger.debug(f"Collected {num_mono_right} right eye monocular references.")
+    logger.debug(f"Collected {num_mono_left} left eye monocular references.")
 
     return (
         matched_binocular_data,
diff --git a/pupil_src/shared_modules/gaze_producer/controller/calculate_all_controller.py b/pupil_src/shared_modules/gaze_producer/controller/calculate_all_controller.py
index 8545db742e..d9aac8e34e 100644
--- a/pupil_src/shared_modules/gaze_producer/controller/calculate_all_controller.py
+++ b/pupil_src/shared_modules/gaze_producer/controller/calculate_all_controller.py
@@ -29,25 +29,22 @@ def __init__(
 
     def calculate_all(self):
         """
-        (Re)Calculate all calibrations and gaze mappings with their respective
-        current settings. If there are no reference locations in the storage,
-        first the current reference detector is run.
+        Detect reference locations if none available. Then (re)calculate all
+        calibrations and gaze mappers.
         """
-        if self.does_detect_references:
+        if self._reference_location_storage.is_empty:
             task = self._reference_detection_controller.start_detection()
             task.add_observer("on_completed", self._on_reference_detection_completed)
         else:
             self._calculate_all_calibrations()
 
-    @property
-    def does_detect_references(self):
+    def calculate_all_if_references_available(self):
         """
-        True if the controller would first detect reference locations in calculate_all()
+        (Re)calculate all calibrations and gaze mappers if reference locations are
+        available.
         """
-        at_least_one_reference_location = any(
-            True for _ in self._reference_location_storage
-        )
-        return not at_least_one_reference_location
+        if not self._reference_location_storage.is_empty:
+            self._calculate_all_calibrations()
 
     def _on_reference_detection_completed(self, _):
         self._calculate_all_calibrations()
diff --git a/pupil_src/shared_modules/gaze_producer/controller/calibration_controller.py b/pupil_src/shared_modules/gaze_producer/controller/calibration_controller.py
index 57349a678d..a2f6f951b6 100644
--- a/pupil_src/shared_modules/gaze_producer/controller/calibration_controller.py
+++ b/pupil_src/shared_modules/gaze_producer/controller/calibration_controller.py
@@ -51,7 +51,9 @@ def on_calibration_completed(status_and_result):
         )
         task.add_observer("on_completed", on_calibration_completed)
         task.add_observer("on_exception", tasklib.raise_exception)
-        self._task_manager.add_task(task)
+        self._task_manager.add_task(
+            task, identifier=f"{calibration.unique_id}-calibration"
+        )
         return task
 
     def on_calibration_computed(self, calibration):
diff --git a/pupil_src/shared_modules/gaze_producer/controller/gaze_mapper_controller.py b/pupil_src/shared_modules/gaze_producer/controller/gaze_mapper_controller.py
index 3482883974..cbed9189d1 100644
--- a/pupil_src/shared_modules/gaze_producer/controller/gaze_mapper_controller.py
+++ b/pupil_src/shared_modules/gaze_producer/controller/gaze_mapper_controller.py
@@ -53,15 +53,15 @@ def calculate(self, gaze_mapper):
         if calibration is None:
             self._abort_calculation(
                 gaze_mapper,
-                "The calibration was not found for the gaze mapper '{}', "
-                "please select a different calibration!".format(gaze_mapper.name),
+                "The calibration was not found for the gaze mapper "
+                f"'{gaze_mapper.name}', please select a different calibration!",
             )
             return None
         if calibration.params is None:
             self._abort_calculation(
                 gaze_mapper,
-                "You first need to calculate calibration '{}' before calculating the "
-                "mapper '{}'".format(calibration.name, gaze_mapper.name),
+                f"You first need to calculate calibration '{calibration.name}' before "
+                f"calculating the mapper '{gaze_mapper.name}'",
             )
             return None
         try:
@@ -69,8 +69,8 @@ def calculate(self, gaze_mapper):
         except worker.map_gaze.NotEnoughPupilData:
             self._abort_calculation(gaze_mapper, "There is no pupil data to be mapped!")
             return None
-        self._task_manager.add_task(task)
-        logger.info("Start gaze mapping for '{}'".format(gaze_mapper.name))
+        self._task_manager.add_task(task, identifier=f"{gaze_mapper.unique_id}-mapping")
+        logger.info(f"Start gaze mapping for '{gaze_mapper.name}'")
 
     def _abort_calculation(self, gaze_mapper, error_message):
         logger.error(error_message)
@@ -92,7 +92,7 @@ def _create_mapping_task(self, gaze_mapper, calibration):
         task = worker.map_gaze.create_task(gaze_mapper, calibration)
 
         def on_yield_gaze(mapped_gaze_ts_and_data):
-            gaze_mapper.status = "Mapping {:.0f}% complete".format(task.progress * 100)
+            gaze_mapper.status = f"Mapping {task.progress * 100:.0f}% complete"
             for timestamp, gaze_datum in mapped_gaze_ts_and_data:
                 gaze_mapper.gaze.append(gaze_datum)
                 gaze_mapper.gaze_ts.append(timestamp)
@@ -153,24 +153,28 @@ def on_gaze_mapping_calculated(self, gaze_mapper):
     def validate_gaze_mapper(self, gaze_mapper):
         def validation_completed(accuracy_and_precision):
             accuracy, precision = accuracy_and_precision
-            gaze_mapper.accuracy_result = "{:.1f}° from {} / {} samples".format(
-                accuracy.result, accuracy.num_used, accuracy.num_total
+            gaze_mapper.accuracy_result = (
+                f"{accuracy.result:.1f}° from {accuracy.num_used} / "
+                f"{accuracy.num_total} samples"
             )
-            gaze_mapper.precision_result = "{:.1f}° from {} / {} samples".format(
-                precision.result, precision.num_used, precision.num_total
+            gaze_mapper.precision_result = (
+                f"{precision.result:.1f}° from {precision.num_used} / "
+                f"{precision.num_total} samples"
             )
 
         calibration = self.get_valid_calibration_or_none(gaze_mapper)
 
         if calibration is None:
             logger.error(
-                f"Could not validate gaze mapper {gaze_mapper.name}; Calibration was not found, please select a different calibration."
+                f"Could not validate gaze mapper {gaze_mapper.name};"
+                " Calibration was not found, please select a different calibration."
             )
             return
 
         if calibration.params is None:
             logger.error(
-                f"Could not validate gaze mapper {gaze_mapper.name}; You first need to calculate calibration '{calibration.name}'"
+                f"Could not validate gaze mapper {gaze_mapper.name};"
+                " You first need to calculate calibration '{calibration.name}'"
             )
             return
 
@@ -179,7 +183,9 @@ def validation_completed(accuracy_and_precision):
         )
         task.add_observer("on_completed", validation_completed)
         task.add_observer("on_exception", tasklib.raise_exception)
-        self._task_manager.add_task(task)
+        self._task_manager.add_task(
+            task, identifier=f"{gaze_mapper.unique_id}-validating"
+        )
 
     def get_valid_calibration_or_none(self, gaze_mapper):
         return self._calibration_storage.get_or_none(gaze_mapper.calibration_unique_id)
diff --git a/pupil_src/shared_modules/gaze_producer/controller/reference_location_controllers.py b/pupil_src/shared_modules/gaze_producer/controller/reference_location_controllers.py
index fd37a94539..19e141a326 100644
--- a/pupil_src/shared_modules/gaze_producer/controller/reference_location_controllers.py
+++ b/pupil_src/shared_modules/gaze_producer/controller/reference_location_controllers.py
@@ -41,7 +41,9 @@ def on_detection_completed(_):
         )
         self._detection_task.add_observer("on_yield", on_detection_yields)
         self._detection_task.add_observer("on_completed", on_detection_completed)
-        self._task_manager.add_task(self._detection_task)
+        self._task_manager.add_task(
+            self._detection_task, identifier="reference_detection"
+        )
         return self._detection_task
 
     def on_detection_started(self, detection_task):
diff --git a/pupil_src/shared_modules/gaze_producer/gaze_from_offline_calibration.py b/pupil_src/shared_modules/gaze_producer/gaze_from_offline_calibration.py
index 6b925f3247..731d0aa173 100644
--- a/pupil_src/shared_modules/gaze_producer/gaze_from_offline_calibration.py
+++ b/pupil_src/shared_modules/gaze_producer/gaze_from_offline_calibration.py
@@ -12,10 +12,9 @@
 from gaze_producer import controller, model
 from gaze_producer import ui as plugin_ui
 from gaze_producer.gaze_producer_base import GazeProducerBase
-from observable import Observable
 from plugin_timeline import PluginTimeline
 from pupil_recording import PupilRecording
-from tasklib.manager import PluginTaskManager
+from tasklib.manager import UniqueTaskManager
 
 
 # IMPORTANT: GazeProducerBase needs to be THE LAST in the list of bases, otherwise
@@ -37,7 +36,7 @@ def __init__(self, g_pool):
 
         self.inject_plugin_dependencies()
 
-        self._task_manager = PluginTaskManager(plugin=self)
+        self._task_manager = UniqueTaskManager(plugin=self)
 
         self._recording_uuid = PupilRecording(g_pool.rec_dir).meta_info.recording_uuid
 
@@ -50,26 +49,31 @@ def __init__(self, g_pool):
             "pupil_positions", g_pool.rec_dir, plugin=self
         )
         self._pupil_changed_listener.add_observer(
-            "on_data_changed", self._calculate_all_controller.calculate_all
+            "on_data_changed",
+            self._calculate_all_controller.calculate_all_if_references_available,
         )
 
     def _setup_storages(self):
         self._reference_location_storage = model.ReferenceLocationStorage(
-            self.g_pool.rec_dir, plugin=self
+            self.g_pool.rec_dir
         )
         self._calibration_storage = model.CalibrationStorage(
             rec_dir=self.g_pool.rec_dir,
-            plugin=self,
             get_recording_index_range=self._recording_index_range,
             recording_uuid=self._recording_uuid,
         )
         self._gaze_mapper_storage = model.GazeMapperStorage(
             self._calibration_storage,
             rec_dir=self.g_pool.rec_dir,
-            plugin=self,
             get_recording_index_range=self._recording_index_range,
         )
 
+    def cleanup(self):
+        super().cleanup()
+        self._reference_location_storage.save_to_disk()
+        self._calibration_storage.save_to_disk()
+        self._gaze_mapper_storage.save_to_disk()
+
     def _setup_controllers(self):
         self._reference_detection_controller = controller.ReferenceDetectionController(
             self._task_manager, self._reference_location_storage
@@ -203,8 +207,9 @@ def _current_trim_mark_range(self):
 
     def _index_range_as_str(self, index_range):
         from_index, to_index = index_range
-        return "{} - {}".format(
-            self._index_time_as_str(from_index), self._index_time_as_str(to_index)
+        return (
+            f"{self._index_time_as_str(from_index)} - "
+            f"{self._index_time_as_str(to_index)}"
         )
 
     def _index_time_as_str(self, index):
@@ -213,4 +218,4 @@ def _index_time_as_str(self, index):
         time = ts - min_ts
         minutes = abs(time // 60)  # abs because it's sometimes -0
         seconds = round(time % 60)
-        return "{:02.0f}:{:02.0f}".format(minutes, seconds)
+        return f"{minutes:02.0f}:{seconds:02.0f}"
diff --git a/pupil_src/shared_modules/gaze_producer/model/calibration.py b/pupil_src/shared_modules/gaze_producer/model/calibration.py
index 8f3e6f1df9..76c74a833b 100644
--- a/pupil_src/shared_modules/gaze_producer/model/calibration.py
+++ b/pupil_src/shared_modules/gaze_producer/model/calibration.py
@@ -51,14 +51,6 @@ def __init__(
         self.__is_offline_calibration = is_offline_calibration
         self.__calib_params = calib_params
 
-        # Assert all properties are consistent
-        try:
-            self.__assert_property_consistency()
-        except ValueError:
-            raise
-        except Exception as err:
-            raise ValueError(str(err))
-
     @property
     def is_offline_calibration(self) -> bool:
         return self.__is_offline_calibration
@@ -79,12 +71,6 @@ def update(
             self.__is_offline_calibration = is_offline_calibration
         if calib_params is not ...:
             self.__calib_params = calib_params
-        try:
-            self.__assert_property_consistency()
-        except ValueError:
-            raise
-        except Exception as err:
-            raise ValueError(str(err))
 
     @staticmethod
     def from_dict(dict_: dict) -> "Calibration":
@@ -98,7 +84,6 @@ def from_dict(dict_: dict) -> "Calibration":
 
     @property
     def as_dict(self) -> dict:
-        self.__assert_property_consistency()  # sanity check
         dict_ = {k: v(self) for (k, v) in self.__schema}
         return dict_
 
@@ -128,12 +113,3 @@ def as_tuple(self):
         ("is_offline_calibration", lambda self: self.__is_offline_calibration),
         ("calib_params", lambda self: self.__calib_params),
     )
-
-    def __assert_property_consistency(self):
-        if self.__is_offline_calibration:
-            pass
-        else:
-            if self.__calib_params is not None:
-                raise ValueError(
-                    f"Unexpected calib_params argument for pre-recorded calibration"
-                )
diff --git a/pupil_src/shared_modules/gaze_producer/model/calibration_storage.py b/pupil_src/shared_modules/gaze_producer/model/calibration_storage.py
index c1a03d5f46..04314f0916 100644
--- a/pupil_src/shared_modules/gaze_producer/model/calibration_storage.py
+++ b/pupil_src/shared_modules/gaze_producer/model/calibration_storage.py
@@ -20,7 +20,12 @@
 from storage import Storage
 from gaze_producer import model
 from observable import Observable
-from gaze_mapping import default_gazer_class, registered_gazer_labels_by_class_names
+from gaze_mapping import (
+    default_gazer_class,
+    registered_gazer_classes,
+    user_selectable_gazer_classes,
+    gazer_classes_by_class_name,
+)
 from gaze_mapping.notifications import (
     CalibrationSetupNotification,
     CalibrationResultNotification,
@@ -33,8 +38,7 @@
 class CalibrationStorage(Storage, Observable):
     _calibration_suffix = "plcal"
 
-    def __init__(self, rec_dir, plugin, get_recording_index_range, recording_uuid):
-        super().__init__(plugin)
+    def __init__(self, rec_dir, get_recording_index_range, recording_uuid):
         self._rec_dir = rec_dir
         self._get_recording_index_range = get_recording_index_range
         self._recording_uuid = str(recording_uuid)
@@ -59,7 +63,7 @@ def create_default_calibration(self):
         )
 
     def __create_prerecorded_calibration(
-        self, result_notification: CalibrationResultNotification
+        self, number: int, result_notification: CalibrationResultNotification
     ):
         timestamp = result_notification.timestamp
 
@@ -68,7 +72,11 @@ def __create_prerecorded_calibration(
         # the easiest datum that differs between calibrations but is the same
         # for every start
         unique_id = model.Calibration.create_unique_id_from_string(str(timestamp))
-        name = make_unique.by_number_at_end("Recorded Calibration", self.item_names)
+
+        name = "Recorded Calibration"
+        if number > 1:
+            name += f" {number}"
+
         return model.Calibration(
             unique_id=unique_id,
             name=name,
@@ -76,7 +84,7 @@ def __create_prerecorded_calibration(
             gazer_class_name=result_notification.gazer_class_name,
             frame_index_range=self._get_recording_index_range(),
             minimum_confidence=0.8,
-            is_offline_calibration=True,
+            is_offline_calibration=False,
             status="Not calculated yet",
             calib_params=result_notification.params,
         )
@@ -89,14 +97,33 @@ def duplicate_calibration(self, calibration):
         new_calibration.unique_id = model.Calibration.create_new_unique_id()
         return new_calibration
 
-    def add(self, calibration):
-        if any(c.unique_id == calibration.unique_id for c in self._calibrations):
+    def add(self, calibration, overwrite=False):
+        for calib in self._calibrations.copy():
+            if calib.unique_id != calibration.unique_id:
+                continue
+            if overwrite:
+                self._calibrations.remove(calib)
+                break
             logger.warning(
                 f"Did not add calibration {calibration.name} ({calibration.unique_id})"
                 " because it is already in the storage. Currently in storage:\n"
                 + "\n".join(f"- {c.name} ({c.unique_id})" for c in self._calibrations)
             )
             return
+        is_calib_editable = (
+            self._from_same_recording(calibration)
+            and calibration.is_offline_calibration
+        )
+        if is_calib_editable:
+            available_gazer_classes = user_selectable_gazer_classes()
+        else:
+            available_gazer_classes = registered_gazer_classes()
+        gazer_class_names = gazer_classes_by_class_name(available_gazer_classes).keys()
+        if calibration.gazer_class_name not in gazer_class_names:
+            logger.warning(
+                f"Did not add calibration {calibration.name} ({calibration.unique_id}) because gaze mapping method ({calibration.gazer_class_name}) is not available."
+            )
+            return
         self._calibrations.append(calibration)
         self._calibrations.sort(key=lambda c: c.name)
 
@@ -161,6 +188,7 @@ def _load_calibration_from_file(self, file_name):
 
     def _load_recorded_calibrations(self):
         notifications = fm.load_pldata_file(self._rec_dir, "notify")
+        counter = 1
         for topic, data in zip(notifications.topics, notifications.data):
             if topic.startswith("notify."):
                 # Remove "notify." prefix
@@ -183,9 +211,10 @@ def _load_recorded_calibrations(self):
                 logger.debug(str(err))
                 continue
             calibration = self.__create_prerecorded_calibration(
-                result_notification=note
+                number=counter, result_notification=note
             )
-            self.add(calibration)
+            self.add(calibration, overwrite=True)
+            counter += 1
 
     def save_to_disk(self):
         os.makedirs(self._calibration_folder, exist_ok=True)
diff --git a/pupil_src/shared_modules/gaze_producer/model/gaze_mapper_storage.py b/pupil_src/shared_modules/gaze_producer/model/gaze_mapper_storage.py
index 49df0809ab..4469dc180b 100644
--- a/pupil_src/shared_modules/gaze_producer/model/gaze_mapper_storage.py
+++ b/pupil_src/shared_modules/gaze_producer/model/gaze_mapper_storage.py
@@ -23,8 +23,8 @@
 
 
 class GazeMapperStorage(SingleFileStorage, Observable):
-    def __init__(self, calibration_storage, rec_dir, plugin, get_recording_index_range):
-        super().__init__(rec_dir, plugin)
+    def __init__(self, calibration_storage, rec_dir, get_recording_index_range):
+        super().__init__(rec_dir)
         self._calibration_storage = calibration_storage
         self._get_recording_index_range = get_recording_index_range
         self._gaze_mappers = []
diff --git a/pupil_src/shared_modules/gaze_producer/model/legacy/calibration_storage_updater.py b/pupil_src/shared_modules/gaze_producer/model/legacy/calibration_storage_updater.py
index c353808b91..6c7388322f 100644
--- a/pupil_src/shared_modules/gaze_producer/model/legacy/calibration_storage_updater.py
+++ b/pupil_src/shared_modules/gaze_producer/model/legacy/calibration_storage_updater.py
@@ -33,7 +33,7 @@ def update_offline_calibrations_to_latest_version(cls, rec_dir):
         if not calib_dir.is_dir():
             return  # TODO: Raise exception - "calibrations" must be a directory
 
-        for calib_path in sorted(calib_dir.glob("*.plcal")):
+        for calib_path in sorted(calib_dir.glob("[!.]*.plcal")):
             calib_dict = fm.load_object(calib_path)
             version = calib_dict.get("version", None)
             data = calib_dict.get("data", None)
diff --git a/pupil_src/shared_modules/gaze_producer/model/reference_location_storage.py b/pupil_src/shared_modules/gaze_producer/model/reference_location_storage.py
index fa39caf984..79531781ec 100644
--- a/pupil_src/shared_modules/gaze_producer/model/reference_location_storage.py
+++ b/pupil_src/shared_modules/gaze_producer/model/reference_location_storage.py
@@ -19,8 +19,8 @@
 
 
 class ReferenceLocationStorage(SingleFileStorage, Observable):
-    def __init__(self, rec_dir, plugin):
-        super().__init__(rec_dir, plugin)
+    def __init__(self, rec_dir):
+        super().__init__(rec_dir)
         self._reference_locations = {}
         self._load_from_disk()
 
diff --git a/pupil_src/shared_modules/gaze_producer/ui/calibration_menu.py b/pupil_src/shared_modules/gaze_producer/ui/calibration_menu.py
index 07f59a19b2..8c6354ab5e 100644
--- a/pupil_src/shared_modules/gaze_producer/ui/calibration_menu.py
+++ b/pupil_src/shared_modules/gaze_producer/ui/calibration_menu.py
@@ -13,7 +13,11 @@
 from pyglui import ui
 
 from gaze_producer import ui as plugin_ui
-from gaze_mapping import registered_gazer_labels_by_class_names
+from gaze_mapping import (
+    gazer_labels_by_class_names,
+    registered_gazer_classes,
+    user_selectable_gazer_classes,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -85,12 +89,15 @@ def _create_range_selector(self, calibration):
         )
 
     def _create_mapping_method_selector(self, calibration):
+        gazers = user_selectable_gazer_classes()
+        gazers_map = gazer_labels_by_class_names(gazers)
+
         return ui.Selector(
             "gazer_class_name",
             calibration,
             label="Gaze Mapping",
-            labels=list(registered_gazer_labels_by_class_names().values()),
-            selection=list(registered_gazer_labels_by_class_names().keys()),
+            labels=list(gazers_map.values()),
+            selection=list(gazers_map.keys()),
         )
 
     def _create_min_confidence_slider(self, calibration):
@@ -120,8 +127,10 @@ def _render_ui_calibration_from_other_recording(self, calibration, menu):
         )
 
     def _info_text_for_calibration_from_other_recording(self, calibration):
+        gazers = registered_gazer_classes()
         gazer_class_name = calibration.gazer_class_name
-        gazer_label = registered_gazer_labels_by_class_names()[gazer_class_name]
+        gazer_label = gazer_labels_by_class_names(gazers)[gazer_class_name]
+
         if calibration.params:
             return (
                 f"This {gazer_label} calibration was copied from another recording. "
@@ -139,18 +148,39 @@ def _render_ui_online_calibration(self, calibration, menu):
         menu.append(ui.Info_Text(self._info_text_for_online_calibration(calibration)))
 
     def _info_text_for_online_calibration(self, calibration):
+        gazers = registered_gazer_classes()
         gazer_class_name = calibration.gazer_class_name
-        gazer_label = registered_gazer_labels_by_class_names()[gazer_class_name]
+        gazer_label = gazer_labels_by_class_names(gazers)[gazer_class_name]
+
         return (
             f"This {gazer_label} calibration was created before or during the "
             "recording. It is ready to be used in gaze mappers."
         )
 
     def _on_click_duplicate_button(self):
-        if self._calibration_controller.is_from_same_recording(self.current_item):
-            super()._on_click_duplicate_button()
-        else:
+        if not self._calibration_controller.is_from_same_recording(self.current_item):
             logger.error("Cannot duplicate calibrations from other recordings!")
+            return
+
+        if not self.current_item.is_offline_calibration:
+            logger.error("Cannot duplicate pre-recorded calibrations!")
+            return
+
+        super()._on_click_duplicate_button()
+
+    def _on_click_delete(self):
+        if self.current_item is None:
+            return
+
+        if not self._calibration_controller.is_from_same_recording(self.current_item):
+            logger.error("Cannot delete calibrations from other recordings!")
+            return
+
+        if not self.current_item.is_offline_calibration:
+            logger.error("Cannot delete pre-recorded calibrations!")
+            return
+
+        super()._on_click_delete()
 
     def _on_name_change(self, new_name):
         self._calibration_storage.rename(self.current_item, new_name)
diff --git a/pupil_src/shared_modules/gaze_producer/ui/on_top_menu.py b/pupil_src/shared_modules/gaze_producer/ui/on_top_menu.py
index 2cdafc7329..0ab0479f9d 100644
--- a/pupil_src/shared_modules/gaze_producer/ui/on_top_menu.py
+++ b/pupil_src/shared_modules/gaze_producer/ui/on_top_menu.py
@@ -19,6 +19,7 @@ def __init__(self, calculate_all_controller, reference_location_storage):
         self._calculate_all_button = None
 
         self._calculate_all_controller = calculate_all_controller
+        self._reference_location_storage = reference_location_storage
 
         reference_location_storage.add_observer(
             "add", self._on_reference_storage_changed
@@ -56,7 +57,7 @@ def _create_calculate_all_button(self):
 
     @property
     def _calculate_all_button_label(self):
-        if self._calculate_all_controller.does_detect_references:
+        if self._reference_location_storage.is_empty:
             return "Detect References, Calculate All Calibrations and Mappings"
         else:
             return "Calculate All Calibrations and Mappings"
diff --git a/pupil_src/shared_modules/gaze_producer/ui/storage_edit_menu.py b/pupil_src/shared_modules/gaze_producer/ui/storage_edit_menu.py
index 09eb7e129a..12b8e3284e 100644
--- a/pupil_src/shared_modules/gaze_producer/ui/storage_edit_menu.py
+++ b/pupil_src/shared_modules/gaze_producer/ui/storage_edit_menu.py
@@ -96,6 +96,8 @@ def _on_click_duplicate_button(self):
         self.render()
 
     def _on_click_delete(self):
+        if self.current_item is None:
+            return
         current_index = self.items.index(self.current_item)
         self._storage.delete(self.current_item)
         current_index = min(current_index, len(self.items) - 1)
diff --git a/pupil_src/shared_modules/gaze_producer/worker/create_calibration.py b/pupil_src/shared_modules/gaze_producer/worker/create_calibration.py
index df85b88986..2b3cf1c059 100644
--- a/pupil_src/shared_modules/gaze_producer/worker/create_calibration.py
+++ b/pupil_src/shared_modules/gaze_producer/worker/create_calibration.py
@@ -15,7 +15,11 @@
 import player_methods as pm
 import tasklib.background
 from gaze_producer import model
-from gaze_mapping import registered_gazer_classes_by_class_name, CalibrationError
+from gaze_mapping import (
+    gazer_classes_by_class_name,
+    registered_gazer_classes,
+    CalibrationError,
+)
 from methods import normalize
 
 from .fake_gpool import FakeGPool
@@ -42,6 +46,7 @@ def create_task(calibration, all_reference_locations):
     ]
 
     fake_gpool = FakeGPool.from_g_pool(g_pool)
+    fake_gpool.min_calibration_confidence = calibration.minimum_confidence
 
     args = (
         fake_gpool,
@@ -49,7 +54,7 @@ def create_task(calibration, all_reference_locations):
         ref_dicts_in_calib_range,
         pupil_pos_in_calib_range,
     )
-    name = "Create calibration {}".format(calibration.name)
+    name = f"Create calibration {calibration.name}"
     return tasklib.background.create(name, _create_calibration, args=args)
 
 
@@ -67,7 +72,7 @@ def _create_calibration(
     # This is needed to support user-provided gazers
     fake_gpool.import_runtime_plugins()
 
-    gazers_by_name = registered_gazer_classes_by_class_name()
+    gazers_by_name = gazer_classes_by_class_name(registered_gazer_classes())
 
     try:
         gazer_class = gazers_by_name[gazer_class_name]
diff --git a/pupil_src/shared_modules/gaze_producer/worker/detect_circle_markers.py b/pupil_src/shared_modules/gaze_producer/worker/detect_circle_markers.py
index 633bd71346..5d74d5d014 100644
--- a/pupil_src/shared_modules/gaze_producer/worker/detect_circle_markers.py
+++ b/pupil_src/shared_modules/gaze_producer/worker/detect_circle_markers.py
@@ -95,12 +95,10 @@ def _receive_detections(self):
                 return
             elif topic == "exception":
                 logger.warning(
-                    "Calibration marker detection raised exception:\n{}".format(
-                        msg["reason"]
-                    )
+                    f"Calibration marker detection raised exception:\n{msg['reason']}"
                 )
                 logger.info("Marker detection was interrupted")
-                logger.debug("Reason: {}".format(msg.get("reason", "n/a")))
+                logger.debug(f"Reason: {msg.get('reason', 'n/a')}")
                 self.on_canceled_or_killed()
                 return
 
diff --git a/pupil_src/shared_modules/gaze_producer/worker/map_gaze.py b/pupil_src/shared_modules/gaze_producer/worker/map_gaze.py
index 88c0dd8c9e..2c17309389 100644
--- a/pupil_src/shared_modules/gaze_producer/worker/map_gaze.py
+++ b/pupil_src/shared_modules/gaze_producer/worker/map_gaze.py
@@ -11,7 +11,7 @@
 import file_methods as fm
 import player_methods as pm
 import tasklib
-from gaze_mapping import registered_gazer_classes_by_class_name
+from gaze_mapping import gazer_classes_by_class_name, registered_gazer_classes
 
 from .fake_gpool import FakeGPool
 
@@ -44,7 +44,7 @@ def create_task(gaze_mapper, calibration):
         gaze_mapper.manual_correction_x,
         gaze_mapper.manual_correction_y,
     )
-    name = "Create gaze mapper {}".format(gaze_mapper.name)
+    name = f"Create gaze mapper {gaze_mapper.name}"
     return tasklib.background.create(
         name, _map_gaze, args=args, pass_shared_memory=True,
     )
@@ -60,7 +60,7 @@ def _map_gaze(
     shared_memory,
 ):
     fake_gpool.import_runtime_plugins()
-    gazers_by_name = registered_gazer_classes_by_class_name()
+    gazers_by_name = gazer_classes_by_class_name(registered_gazer_classes())
     gazer_cls = gazers_by_name[gazer_class_name]
     gazer = gazer_cls(fake_gpool, params=gazer_params)
 
diff --git a/pupil_src/shared_modules/gaze_producer/worker/validate_gaze.py b/pupil_src/shared_modules/gaze_producer/worker/validate_gaze.py
index 132aed7ccd..7d650ca301 100644
--- a/pupil_src/shared_modules/gaze_producer/worker/validate_gaze.py
+++ b/pupil_src/shared_modules/gaze_producer/worker/validate_gaze.py
@@ -13,7 +13,7 @@
 from methods import normalize
 import player_methods as pm
 
-from gaze_mapping import registered_gazer_classes_by_class_name
+from gaze_mapping import gazer_classes_by_class_name, registered_gazer_classes
 
 from .fake_gpool import FakeGPool
 
@@ -48,7 +48,7 @@ def create_bg_task(gaze_mapper, calibration, reference_location_storage):
     )
 
     return tasklib.background.create(
-        "validate gaze mapper '{}'".format(gaze_mapper.name), validate, args=args,
+        f"validate gaze mapper '{gaze_mapper.name}'", validate, args=args,
     )
 
 
@@ -61,7 +61,7 @@ def validate(
     refs_in_validation_range,
 ):
     g_pool.import_runtime_plugins()
-    gazers_by_name = registered_gazer_classes_by_class_name()
+    gazers_by_name = gazer_classes_by_class_name(registered_gazer_classes())
     gazer_class = gazers_by_name[gazer_class_name]
 
     pupil_list = pupils_in_validation_range
diff --git a/pupil_src/shared_modules/gl_utils/utils.py b/pupil_src/shared_modules/gl_utils/utils.py
index 96450e62fe..f761a276c9 100644
--- a/pupil_src/shared_modules/gl_utils/utils.py
+++ b/pupil_src/shared_modules/gl_utils/utils.py
@@ -188,6 +188,12 @@ class Coord_System(object):
 
     def __init__(self, left, right, bottom, top):
         super(Coord_System, self).__init__()
+        if left == right:
+            left -= 1
+            right += 1
+        if top == bottom:
+            top -= 1
+            bottom += 1
         self.bounds = left, right, bottom, top
 
     def __enter__(self):
diff --git a/pupil_src/shared_modules/gprof2dot.py b/pupil_src/shared_modules/gprof2dot.py
index 686854dee9..6d8f676e62 100644
--- a/pupil_src/shared_modules/gprof2dot.py
+++ b/pupil_src/shared_modules/gprof2dot.py
@@ -2402,9 +2402,14 @@ def parse_samples(self):
         self.consume()
 
         while not self.lookahead().startswith("CPU"):
-            rank, percent_self, percent_accum, count, traceid, method = (
-                self.lookahead().split()
-            )
+            (
+                rank,
+                percent_self,
+                percent_accum,
+                count,
+                traceid,
+                method,
+            ) = self.lookahead().split()
             self.samples[int(traceid)] = (int(count), method)
             self.consume()
 
diff --git a/pupil_src/shared_modules/head_pose_tracker/ui/offline_head_pose_tracker_timeline.py b/pupil_src/shared_modules/head_pose_tracker/ui/offline_head_pose_tracker_timeline.py
index 72b4d974d3..26f055225d 100644
--- a/pupil_src/shared_modules/head_pose_tracker/ui/offline_head_pose_tracker_timeline.py
+++ b/pupil_src/shared_modules/head_pose_tracker/ui/offline_head_pose_tracker_timeline.py
@@ -95,9 +95,10 @@ def _create_progress_indication(self):
             return RangeElementFrameIdx()
 
     def _on_detection_started(self):
-        self._frame_start, frame_end = (
-            self._general_settings.detection_frame_index_range
-        )
+        (
+            self._frame_start,
+            frame_end,
+        ) = self._general_settings.detection_frame_index_range
         self._frame_count = frame_end - self._frame_start + 1
 
     def _on_storage_changed(self):
@@ -169,9 +170,10 @@ def _on_localization_reset(self):
         self.render_parent_timeline()
 
     def _on_localization_started(self):
-        self._frame_start, frame_end = (
-            self._general_settings.localization_frame_index_range
-        )
+        (
+            self._frame_start,
+            frame_end,
+        ) = self._general_settings.localization_frame_index_range
         self._frame_count = frame_end - self._frame_start + 1
 
     def _on_storage_changed(self):
diff --git a/pupil_src/shared_modules/hololens_relay.py b/pupil_src/shared_modules/hololens_relay.py
index 9f178c76b7..20d06a19dc 100644
--- a/pupil_src/shared_modules/hololens_relay.py
+++ b/pupil_src/shared_modules/hololens_relay.py
@@ -391,9 +391,7 @@ def on_recv(self, socket, ipc_pub):
                 calib_method = "HMD_Calibration_3D"
 
             ipc_pub.notify({"subject": "start_plugin", "name": calib_method})
-            ipc_pub.notify(
-                {"subject": "set_pupil_detection_enabled", "value": True}
-            )
+            ipc_pub.notify({"subject": "set_pupil_detection_enabled", "value": True})
             ipc_pub.notify(
                 {
                     "subject": "eye_process.should_start.{}".format(0),
diff --git a/pupil_src/shared_modules/network_api/controller/frame_publisher_controller.py b/pupil_src/shared_modules/network_api/controller/frame_publisher_controller.py
index fb9bd8d5a7..b54b4ffa27 100644
--- a/pupil_src/shared_modules/network_api/controller/frame_publisher_controller.py
+++ b/pupil_src/shared_modules/network_api/controller/frame_publisher_controller.py
@@ -20,11 +20,8 @@
 
 
 class FramePublisherController(Observable):
-    def on_frame_publisher_did_start(self, format: FrameFormat):
-        logger.debug(f"on_frame_publisher_did_start({format})")
-
-    def on_frame_publisher_did_stop(self):
-        logger.debug(f"on_frame_publisher_did_stop")
+    def on_format_changed(self):
+        logger.debug(f"on_format_changed({self.__frame_format})")
 
     def __init__(self, format="jpeg", **kwargs):
         self.__frame_format = FrameFormat(format)
@@ -33,9 +30,6 @@ def __init__(self, format="jpeg", **kwargs):
     def get_init_dict(self):
         return {"format": self.__frame_format.value}
 
-    def cleanup(self):
-        self.on_frame_publisher_did_stop()
-
     @property
     def frame_format(self):
         return self.__frame_format
@@ -43,7 +37,7 @@ def frame_format(self):
     @frame_format.setter
     def frame_format(self, value):
         self.__frame_format = FrameFormat(value)
-        self.on_frame_publisher_did_start(format=self.__frame_format)
+        self.on_format_changed()
 
     def create_world_frame_dicts_from_frame(self, frame) -> T.List[dict]:
         if not frame:
diff --git a/pupil_src/shared_modules/network_api/network_api_plugin.py b/pupil_src/shared_modules/network_api/network_api_plugin.py
index 488d9aeadc..2047dbd93e 100644
--- a/pupil_src/shared_modules/network_api/network_api_plugin.py
+++ b/pupil_src/shared_modules/network_api/network_api_plugin.py
@@ -11,9 +11,7 @@
 import logging
 
 from plugin import Plugin
-from pyglui import ui
 
-from .model import FrameFormat
 from .controller import FramePublisherController
 from .controller import PupilRemoteController
 from .ui import FramePublisherMenu
@@ -39,12 +37,12 @@ def __init__(self, g_pool, **kwargs):
         # Frame Publisher setup
         self.__frame_publisher = FramePublisherController(**kwargs)
         self.__frame_publisher.add_observer(
-            "on_frame_publisher_did_start", self.on_frame_publisher_did_start
-        )
-        self.__frame_publisher.add_observer(
-            "on_frame_publisher_did_stop", self.on_frame_publisher_did_stop
+            "on_format_changed", self.frame_publisher_announce_current_format
         )
 
+        # Let existing eye-processes know about current frame publishing format
+        self.frame_publisher_announce_current_format()
+
         # Pupil Remote setup
         self.__pupil_remote = PupilRemoteController(g_pool, **kwargs)
         self.__pupil_remote.add_observer(
@@ -65,7 +63,7 @@ def get_init_dict(self):
         }
 
     def cleanup(self):
-        self.__frame_publisher.cleanup()
+        self.frame_publisher_announce_stop()
         self.__frame_publisher = None
         self.__pupil_remote.cleanup()
         self.__pupil_remote = None
@@ -105,16 +103,21 @@ def on_notify(self, notification):
             Any other notification received though the reqrepl port.
         """
         if notification["subject"].startswith("eye_process.started"):
-            # trigger notification
-            self.__frame_publisher.frame_format = self.__frame_publisher.frame_format
+            # Let newly started eye-processes know about current frame publishing format
+            self.frame_publisher_announce_current_format()
         elif notification["subject"] == "frame_publishing.set_format":
             # update format and trigger notification
             self.__frame_publisher.frame_format = notification["format"]
 
-    def on_frame_publisher_did_start(self, format: FrameFormat):
-        self.notify_all({"subject": "frame_publishing.started", "format": format.value})
+    def frame_publisher_announce_current_format(self, *_):
+        self.notify_all(
+            {
+                "subject": "frame_publishing.started",
+                "format": self.__frame_publisher.frame_format.value,
+            }
+        )
 
-    def on_frame_publisher_did_stop(self):
+    def frame_publisher_announce_stop(self):
         self.notify_all({"subject": "frame_publishing.stopped"})
 
     def on_pupil_remote_server_did_start(self, address: str):
diff --git a/pupil_src/shared_modules/plugin.py b/pupil_src/shared_modules/plugin.py
index b96b77c297..0d2746e737 100644
--- a/pupil_src/shared_modules/plugin.py
+++ b/pupil_src/shared_modules/plugin.py
@@ -493,7 +493,7 @@ def import_runtime_plugins(plugin_dir):
                         and issubclass(member, Plugin)
                         and member.__name__ != "Plugin"
                     ):
-                        logger.info("Added: {}".format(member))
+                        logger.debug("Added: {}".format(member))
                         runtime_plugins.append(member)
             except Exception as e:
                 logger.warning("Failed to load '{}'. Reason: '{}' ".format(d, e))
diff --git a/pupil_src/shared_modules/pupil_detector_plugins/visualizer_2d.py b/pupil_src/shared_modules/pupil_detector_plugins/visualizer_2d.py
index a7b50ee70b..4252e87a0c 100644
--- a/pupil_src/shared_modules/pupil_detector_plugins/visualizer_2d.py
+++ b/pupil_src/shared_modules/pupil_detector_plugins/visualizer_2d.py
@@ -29,11 +29,15 @@ def draw_ellipse(
             arcEnd=360,
             delta=8,
         )
-    except ValueError:
-        # Happens when converting 'nan' to int
-        # TODO: Investigate why results are sometimes 'nan'
-        logger.debug(f"WARN: trying to draw ellipse with 'NaN' data: {ellipse}")
-        return
+    except Exception as e:
+        # Known issues:
+        #   - There are reports of negative eye_ball axes when drawing the 3D eyeball
+        #     outline, which will raise cv2.error. TODO: Investigate cause in detectors.
+        logger.debug(
+            "Error drawing ellipse! Skipping...\n"
+            f"ellipse: {ellipse}\n"
+            f"{type(e)}: {e}"
+        )
 
     draw_polyline(pts, thickness, RGBA(*rgba))
     if draw_center:
@@ -43,6 +47,12 @@ def draw_ellipse(
 
 
 def draw_eyeball_outline(pupil_detection_result_3d):
+    if pupil_detection_result_3d["model_confidence"] <= 0.0:
+        # NOTE: if 'model_confidence' == 0, some values of the 'projected_sphere' might
+        # be 'nan', which will cause cv2.ellipse to crash.
+        # TODO: Fix in detectors.
+        return
+
     draw_ellipse(
         ellipse=pupil_detection_result_3d["projected_sphere"],
         rgba=(0, 0.9, 0.1, pupil_detection_result_3d["model_confidence"]),
diff --git a/pupil_src/shared_modules/pupil_recording/update/__init__.py b/pupil_src/shared_modules/pupil_recording/update/__init__.py
index 831d6e05ce..d663ab3ca2 100644
--- a/pupil_src/shared_modules/pupil_recording/update/__init__.py
+++ b/pupil_src/shared_modules/pupil_recording/update/__init__.py
@@ -80,6 +80,7 @@ def update_recording(rec_dir: str):
 
     # Update offline calibrations to latest calibration model version
     from gaze_producer.model.legacy import update_offline_calibrations_to_latest_version
+
     update_offline_calibrations_to_latest_version(rec_dir)
 
 
diff --git a/pupil_src/shared_modules/recorder.py b/pupil_src/shared_modules/recorder.py
index 527c27c508..bd85813abe 100644
--- a/pupil_src/shared_modules/recorder.py
+++ b/pupil_src/shared_modules/recorder.py
@@ -31,7 +31,10 @@
 from pupil_recording.info import Version
 from pupil_recording.info import RecordingInfoFile
 
-from gaze_mapping.notifications import CalibrationSetupNotification, CalibrationResultNotification
+from gaze_mapping.notifications import (
+    CalibrationSetupNotification,
+    CalibrationResultNotification,
+)
 
 # from scipy.interpolate import UnivariateSpline
 from plugin import System_Plugin_Base
@@ -350,7 +353,10 @@ def start(self):
         else:
             self.writer = MPEG_Writer(self.video_path, start_time_synced)
 
-        calibration_data_notification_classes = [CalibrationSetupNotification, CalibrationResultNotification]
+        calibration_data_notification_classes = [
+            CalibrationSetupNotification,
+            CalibrationResultNotification,
+        ]
         writer = PLData_Writer(self.rec_path, "notify")
 
         for note_class in calibration_data_notification_classes:
diff --git a/pupil_src/shared_modules/remote_recorder.py b/pupil_src/shared_modules/remote_recorder.py
index d6fa0f2fd3..c1f3a18af2 100644
--- a/pupil_src/shared_modules/remote_recorder.py
+++ b/pupil_src/shared_modules/remote_recorder.py
@@ -74,8 +74,7 @@ def __init__(self, num_states_changed_callback):
 
         self._attached_rec_states = {}
         self._network = ndsi.Network(
-            formats={ndsi.DataFormat.V3},
-            callbacks=(self.on_event,)
+            formats={ndsi.DataFormat.V3}, callbacks=(self.on_event,)
         )
         self._network.start()
 
diff --git a/pupil_src/shared_modules/stdlib_utils.py b/pupil_src/shared_modules/stdlib_utils.py
index 16aed138bd..169f619b90 100644
--- a/pupil_src/shared_modules/stdlib_utils.py
+++ b/pupil_src/shared_modules/stdlib_utils.py
@@ -26,9 +26,13 @@ class sliceable_deque(collections.deque):
     """
     deque subclass with support for slicing.
     """
+
     def __getitem__(self, index):
         if isinstance(index, slice):
-            return type(self)(itertools.islice(self, index.start, index.stop, index.step), maxlen=self.maxlen)
+            return type(self)(
+                itertools.islice(self, index.start, index.stop, index.step),
+                maxlen=self.maxlen,
+            )
         return collections.deque.__getitem__(self, index)
 
 
@@ -39,8 +43,12 @@ def __getitem__(self, index):
 
 
 class unique(collections.abc.Iterable):
-
-    def __init__(self, it: typing.Iterable, key: Unique_Key_Getter=..., select: Unique_Select=...):
+    def __init__(
+        self,
+        it: typing.Iterable,
+        key: Unique_Key_Getter = ...,
+        select: Unique_Select = ...,
+    ):
         self._it = list(it)
         self._key = key if key is not ... else lambda elem: elem
         self._select = select if select is not ... else lambda x, y: x
diff --git a/pupil_src/shared_modules/storage.py b/pupil_src/shared_modules/storage.py
index d76691f08b..d3cc575d7b 100644
--- a/pupil_src/shared_modules/storage.py
+++ b/pupil_src/shared_modules/storage.py
@@ -60,12 +60,17 @@ def create_unique_id_from_string(string):
 
 
 class Storage(abc.ABC):
-    def __init__(self, plugin):
-        plugin.add_observer("cleanup", self._on_cleanup)
-
     def __iter__(self):
         return iter(self.items)
 
+    @property
+    def is_empty(self):
+        try:
+            next(iter(self))
+            return False
+        except StopIteration:
+            return True
+
     @abc.abstractmethod
     def add(self, item):
         pass
@@ -111,9 +116,6 @@ def _load_data_from_file(self, filepath):
             return None
         return dict_representation.get("data", None)
 
-    def _on_cleanup(self):
-        self.save_to_disk()
-
     @staticmethod
     def get_valid_filename(file_name):
         """
@@ -138,8 +140,7 @@ class SingleFileStorage(Storage, abc.ABC):
     Storage that can save and load all items from / to a single file
     """
 
-    def __init__(self, rec_dir, plugin):
-        super().__init__(plugin)
+    def __init__(self, rec_dir):
         self._rec_dir = rec_dir
 
     def save_to_disk(self):
diff --git a/pupil_src/shared_modules/surface_tracker/background_tasks.py b/pupil_src/shared_modules/surface_tracker/background_tasks.py
index 120f1210f9..7885a241e6 100644
--- a/pupil_src/shared_modules/surface_tracker/background_tasks.py
+++ b/pupil_src/shared_modules/surface_tracker/background_tasks.py
@@ -272,9 +272,10 @@ def save_surface_statisics_to_file(self):
                 logger.warning("Could not make metrics dir {}".format(self.metrics_dir))
                 return
 
-        self.gaze_on_surfaces, self.fixations_on_surfaces = (
-            self._map_gaze_and_fixations()
-        )
+        (
+            self.gaze_on_surfaces,
+            self.fixations_on_surfaces,
+        ) = self._map_gaze_and_fixations()
 
         self._export_surface_visibility()
         self._export_surface_gaze_distribution()
diff --git a/pupil_src/shared_modules/surface_tracker/surface_file_store.py b/pupil_src/shared_modules/surface_tracker/surface_file_store.py
index a30b2313a9..5463ee253d 100644
--- a/pupil_src/shared_modules/surface_tracker/surface_file_store.py
+++ b/pupil_src/shared_modules/surface_tracker/surface_file_store.py
@@ -64,24 +64,34 @@ def read_surfaces_from_file(self, surface_class) -> typing.Iterator[Surface]:
             file_path=self.file_path,
             serializer=self.serializer,
             surface_class=surface_class,
-            should_skip_on_invalid=False
+            should_skip_on_invalid=False,
         )
 
     def write_surfaces_to_file(self, surfaces: typing.Iterator[Surface]):
         dict_from_surface = self.serializer.dict_from_surface
-        serialized_surfaces = [ dict_from_surface(surface) for surface in surfaces if surface.defined]
+        serialized_surfaces = [
+            dict_from_surface(surface) for surface in surfaces if surface.defined
+        ]
         surface_definitions = self._persistent_dict_class(self.file_path)
         surface_definitions["surfaces"] = serialized_surfaces
         surface_definitions.save()
 
     # Protected API
 
-    def _read_surfaces_from_file_path(self, file_path: str, serializer: _Surface_Serializer_Base, surface_class, should_skip_on_invalid: bool = False) -> typing.Iterator[Surface]:
+    def _read_surfaces_from_file_path(
+        self,
+        file_path: str,
+        serializer: _Surface_Serializer_Base,
+        surface_class,
+        should_skip_on_invalid: bool = False,
+    ) -> typing.Iterator[Surface]:
         # TODO: Assert surface_class is a class, and is a Surface subclass
 
         def surface_from_dict(surface_dict: dict) -> typing.Optional[Surface]:
             try:
-                return serializer.surface_from_dict(surface_definition=surface_dict, surface_class=surface_class)
+                return serializer.surface_from_dict(
+                    surface_definition=surface_dict, surface_class=surface_class
+                )
             except InvalidSurfaceDefinition:
                 if should_skip_on_invalid:
                     return None
@@ -137,7 +147,7 @@ def read_surfaces_from_file(self, surface_class) -> typing.Iterator[Surface]:
             file_path=self.__legacy_file_path,
             serializer=self.serializer,
             surface_class=surface_class,
-            should_skip_on_invalid=True  # Since this file might contain older surface definitions, those can be skipped
+            should_skip_on_invalid=True,  # Since this file might contain older surface definitions, those can be skipped
         )
 
     # Private
@@ -165,7 +175,9 @@ def __init__(self, parent_dir, **kwargs):
 
         # Pre-computed properties
         self.__supported_versions = tuple(sorted(self.__versioned_file_stores.keys()))
-        self.__migration_step_sequence = tuple(zip(self.__supported_versions, self.__supported_versions[1:]))
+        self.__migration_step_sequence = tuple(
+            zip(self.__supported_versions, self.__supported_versions[1:])
+        )
 
     @property
     def file_name(self) -> str:
@@ -183,10 +195,16 @@ def read_surfaces_from_file(self, surface_class) -> typing.Iterator[Surface]:
 
         # Perform all migrations
         for source_version, target_version in self.__migration_step_sequence:
-            migration_proc = self.__migration_procedure(surface_class=surface_class, source_version=source_version, target_version=target_version)
+            migration_proc = self.__migration_procedure(
+                surface_class=surface_class,
+                source_version=source_version,
+                target_version=target_version,
+            )
             migration_proc()
 
-        return self.__file_store_latest.read_surfaces_from_file(surface_class=surface_class)
+        return self.__file_store_latest.read_surfaces_from_file(
+            surface_class=surface_class
+        )
 
     def write_surfaces_to_file(self, surfaces: typing.Iterator[Surface]):
         self.__file_store_latest.write_surfaces_to_file(surfaces=surfaces)
@@ -198,7 +216,9 @@ def __file_store_latest(self) -> _Surface_File_Store_Base:
         latest_version = self.__supported_versions[-1]
         return self.__versioned_file_stores[latest_version]
 
-    def __migration_procedure(self, surface_class, source_version: Version, target_version: Version) -> Migration_Procedure:
+    def __migration_procedure(
+        self, surface_class, source_version: Version, target_version: Version
+    ) -> Migration_Procedure:
         # Handle any special-case migrations here
         if (source_version, target_version) == (0, 1):
             return functools.partial(
@@ -216,7 +236,9 @@ def __migration_procedure(self, surface_class, source_version: Version, target_v
             target_version=target_version,
         )
 
-    def __simple_rewrite_migration(self, surface_class, source_version: Version, target_version: Version):
+    def __simple_rewrite_migration(
+        self, surface_class, source_version: Version, target_version: Version
+    ):
         source_file_store = self.__versioned_file_stores[source_version]
         target_file_store = self.__versioned_file_stores[target_version]
 
@@ -225,10 +247,14 @@ def __simple_rewrite_migration(self, surface_class, source_version: Version, tar
             return
 
         # Otherwise, write the surfaces to the new location with the new format
-        surfaces = source_file_store.read_surfaces_from_file(surface_class=surface_class)
+        surfaces = source_file_store.read_surfaces_from_file(
+            surface_class=surface_class
+        )
         target_file_store.write_surfaces_to_file(surfaces=surfaces)
 
-    def __migration_v00_v01(self, surface_class, source_version: Version, target_version: Version):
+    def __migration_v00_v01(
+        self, surface_class, source_version: Version, target_version: Version
+    ):
         assert source_version == 0
         assert target_version == 1
 
diff --git a/pupil_src/shared_modules/surface_tracker/surface_marker.py b/pupil_src/shared_modules/surface_tracker/surface_marker.py
index 001b1df9c4..7b6f1e7c38 100644
--- a/pupil_src/shared_modules/surface_tracker/surface_marker.py
+++ b/pupil_src/shared_modules/surface_tracker/surface_marker.py
@@ -74,7 +74,7 @@ def create_surface_marker_uid(
 
 
 def _parse_surface_marker_uid_components(
-    uid: Surface_Marker_UID
+    uid: Surface_Marker_UID,
 ) -> typing.Tuple[Surface_Marker_Type, typing.Optional[str], Surface_Marker_TagID]:
     components = str(uid).split(":")
     if len(components) == 2:
@@ -284,7 +284,7 @@ def from_square_tag_detection(detection: dict) -> "Surface_Marker":
 
     @staticmethod
     def from_apriltag_v3_detection(
-        detection: Apriltag_V3_Detection
+        detection: Apriltag_V3_Detection,
     ) -> "Surface_Marker":
         cls = _Apriltag_V3_Marker_Detection
         raw_marker = cls(
diff --git a/pupil_src/shared_modules/surface_tracker/surface_marker_aggregate.py b/pupil_src/shared_modules/surface_tracker/surface_marker_aggregate.py
index f64ea54613..e49b7d6551 100644
--- a/pupil_src/shared_modules/surface_tracker/surface_marker_aggregate.py
+++ b/pupil_src/shared_modules/surface_tracker/surface_marker_aggregate.py
@@ -26,11 +26,14 @@ class Surface_Marker_Aggregate(object):
     """
 
     @staticmethod
-    def property_equality(x: "Surface_Marker_Aggregate", y: "Surface_Marker_Aggregate") -> bool:
+    def property_equality(
+        x: "Surface_Marker_Aggregate", y: "Surface_Marker_Aggregate"
+    ) -> bool:
         def property_dict(x: Surface_Marker_Aggregate) -> dict:
             x_dict = x.__dict__.copy()
             x_dict["_verts_uv"] = x_dict["_verts_uv"].tolist()
             return x_dict
+
         return property_dict(x) == property_dict(y)
 
     def __init__(
diff --git a/pupil_src/shared_modules/surface_tracker/surface_serializer.py b/pupil_src/shared_modules/surface_tracker/surface_serializer.py
index f374f27792..11e4091f89 100644
--- a/pupil_src/shared_modules/surface_tracker/surface_serializer.py
+++ b/pupil_src/shared_modules/surface_tracker/surface_serializer.py
@@ -15,11 +15,15 @@
 import os
 import typing
 
-from .surface import Surface
-from .surface import Surface_Marker_Aggregate
-from .surface_marker import Surface_Marker_UID, Surface_Marker_Type, Surface_Marker_TagID
-from .surface_marker import create_surface_marker_uid, parse_surface_marker_tag_id, parse_surface_marker_type
-
+from .surface import Surface, Surface_Marker_Aggregate
+from .surface_marker import (
+    Surface_Marker_TagID,
+    Surface_Marker_Type,
+    Surface_Marker_UID,
+    create_surface_marker_uid,
+    parse_surface_marker_tag_id,
+    parse_surface_marker_type,
+)
 
 logger = logging.getLogger(__name__)
 
@@ -29,18 +33,21 @@ class InvalidSurfaceDefinition(Exception):
 
 
 class _Surface_Serializer_Base(abc.ABC):
-
     @property
     @abc.abstractmethod
     def version(self) -> int:
         pass
 
     @abc.abstractmethod
-    def dict_from_surface_marker_aggregate(self, surface_marker_aggregate: Surface_Marker_Aggregate) -> dict:
+    def dict_from_surface_marker_aggregate(
+        self, surface_marker_aggregate: Surface_Marker_Aggregate
+    ) -> dict:
         pass
 
     @abc.abstractmethod
-    def surface_marker_aggregate_from_dict(self, surface_marker_aggregate_dict: dict) -> Surface_Marker_Aggregate:
+    def surface_marker_aggregate_from_dict(
+        self, surface_marker_aggregate_dict: dict
+    ) -> Surface_Marker_Aggregate:
         pass
 
     def dict_from_surface(self, surface: Surface) -> dict:
@@ -48,11 +55,11 @@ def dict_from_surface(self, surface: Surface) -> dict:
 
         reg_markers = [
             dict_from_marker_aggregate(marker_aggregate)
-            for marker_aggregate in surface._registered_markers_undist.values() #TODO: Provide a public property for this
+            for marker_aggregate in surface._registered_markers_undist.values()  # TODO: Provide a public property for this
         ]
         registered_markers_dist = [
             dict_from_marker_aggregate(marker_aggregate)
-            for marker_aggregate in surface._registered_markers_dist.values() #TODO: Provide a public property for this
+            for marker_aggregate in surface._registered_markers_dist.values()  # TODO: Provide a public property for this
         ]
         return {
             "version": self.version,
@@ -65,8 +72,12 @@ def dict_from_surface(self, surface: Surface) -> dict:
         }
 
     def surface_from_dict(self, surface_class, surface_definition: dict) -> Surface:
-        assert isinstance(surface_class, type(object)), f"surface_class must be a class: {surface_class}"
-        assert issubclass(surface_class, Surface), f"surface_class must be a subclass of Surface: {surface_class}"
+        assert isinstance(
+            surface_class, type(object)
+        ), f"surface_class must be a class: {surface_class}"
+        assert issubclass(
+            surface_class, Surface
+        ), f"surface_class must be a subclass of Surface: {surface_class}"
 
         expected_version = self.version
         actual_version = surface_definition["version"]
@@ -76,15 +87,17 @@ def surface_from_dict(self, surface_class, surface_definition: dict) -> Surface:
 
         marker_aggregate_from_dict = self.surface_marker_aggregate_from_dict
 
-        marker_aggregates_undist = [marker_aggregate_from_dict(d) for d in surface_definition["reg_markers" ]]
-        marker_aggregates_dist = [marker_aggregate_from_dict(d) for d in surface_definition["registered_markers_dist"]]
+        marker_aggregates_undist = [
+            marker_aggregate_from_dict(d) for d in surface_definition["reg_markers"]
+        ]
+        marker_aggregates_dist = [
+            marker_aggregate_from_dict(d)
+            for d in surface_definition["registered_markers_dist"]
+        ]
+
+        deprecated_definition = surface_definition.get("deprecated", True)
 
-        deprecated_definition = None
-        try:
-            deprecated_definition = surface_definition["deprecated"]
-        except KeyError:
-            pass
-        else:
+        if deprecated_definition:
             logger.warning(
                 "You have loaded an old and deprecated surface definition! "
                 "Please re-define this surface for increased mapping accuracy!"
@@ -104,7 +117,9 @@ class _Surface_Serializer_V00(_Surface_Serializer_Base):
 
     version = 0
 
-    def dict_from_surface_marker_aggregate(self, surface_marker_aggregate: Surface_Marker_Aggregate) -> dict:
+    def dict_from_surface_marker_aggregate(
+        self, surface_marker_aggregate: Surface_Marker_Aggregate
+    ) -> dict:
         id = parse_surface_marker_tag_id(uid=surface_marker_aggregate.uid)
         marker_type = parse_surface_marker_type(uid=surface_marker_aggregate.uid)
         if marker_type != Surface_Marker_Type.SQUARE:
@@ -115,12 +130,14 @@ def dict_from_surface_marker_aggregate(self, surface_marker_aggregate: Surface_M
             verts_uv = [v.tolist() for v in verts_uv]
         return {"id": id, "verts_uv": verts_uv}
 
-    def surface_marker_aggregate_from_dict(self, surface_marker_aggregate_dict: dict) -> Surface_Marker_Aggregate:
+    def surface_marker_aggregate_from_dict(
+        self, surface_marker_aggregate_dict: dict
+    ) -> Surface_Marker_Aggregate:
         tag_id = surface_marker_aggregate_dict["id"]
         uid = create_surface_marker_uid(
             marker_type=Surface_Marker_Type.SQUARE,
             tag_family=None,
-            tag_id=Surface_Marker_TagID(tag_id)
+            tag_id=Surface_Marker_TagID(tag_id),
         )
         verts_uv = surface_marker_aggregate_dict["verts_uv"]
         return Surface_Marker_Aggregate(uid=uid, verts_uv=verts_uv)
@@ -135,8 +152,7 @@ def surface_from_dict(self, surface_class, surface_definition: dict) -> Surface:
         # The format of v00 doesn't store any value for "version" key
         surface_definition["version"] = surface_definition.get("version", self.version)
         return super().surface_from_dict(
-            surface_class=surface_class,
-            surface_definition=surface_definition,
+            surface_class=surface_class, surface_definition=surface_definition
         )
 
 
@@ -144,14 +160,18 @@ class _Surface_Serializer_V01(_Surface_Serializer_Base):
 
     version = 1
 
-    def dict_from_surface_marker_aggregate(self, surface_marker_aggregate: Surface_Marker_Aggregate) -> dict:
+    def dict_from_surface_marker_aggregate(
+        self, surface_marker_aggregate: Surface_Marker_Aggregate
+    ) -> dict:
         uid = str(surface_marker_aggregate.uid)
         verts_uv = surface_marker_aggregate.verts_uv
         if verts_uv is not None:
             verts_uv = [v.tolist() for v in verts_uv]
         return {"uid": uid, "verts_uv": verts_uv}
 
-    def surface_marker_aggregate_from_dict(self, surface_marker_aggregate_dict: dict) -> Surface_Marker_Aggregate:
+    def surface_marker_aggregate_from_dict(
+        self, surface_marker_aggregate_dict: dict
+    ) -> Surface_Marker_Aggregate:
         uid = surface_marker_aggregate_dict["uid"]
         verts_uv = surface_marker_aggregate_dict["verts_uv"]
         return Surface_Marker_Aggregate(uid=uid, verts_uv=verts_uv)
diff --git a/pupil_src/shared_modules/surface_tracker/surface_tracker.py b/pupil_src/shared_modules/surface_tracker/surface_tracker.py
index ad2f1921fc..db3292ba10 100644
--- a/pupil_src/shared_modules/surface_tracker/surface_tracker.py
+++ b/pupil_src/shared_modules/surface_tracker/surface_tracker.py
@@ -74,6 +74,7 @@ def __init__(
         self._edit_surf_verts = []
         self._last_mouse_pos = (0.0, 0.0)
         self.gui = gui.GUI(self)
+        self._ui_heatmap_mode_selector = None
 
         if not isinstance(marker_detector_mode, MarkerDetectorMode):
             # Here we ensure that we pass a proper MarkerDetectorMode
@@ -161,20 +162,19 @@ def _update_ui(self):
             self._per_surface_ui(surface)
 
     def _update_ui_visualization_menu(self):
+        self._ui_heatmap_mode_selector = ui.Selector(
+            "heatmap_mode",
+            self.gui,
+            label="Heatmap Mode",
+            labels=[e.value for e in self.supported_heatmap_modes],
+            selection=[e for e in self.supported_heatmap_modes],
+        )
         self.menu.append(ui.Info_Text(self.ui_info_text))
         self.menu.append(
             ui.Switch("show_marker_ids", self.gui, label="Show Marker IDs")
         )
         self.menu.append(ui.Switch("show_heatmap", self.gui, label="Show Heatmap"))
-        self.menu.append(
-            ui.Selector(
-                "heatmap_mode",
-                self.gui,
-                label="Heatmap Mode",
-                labels=[e.value for e in self.supported_heatmap_modes],
-                selection=[e for e in self.supported_heatmap_modes],
-            )
-        )
+        self.menu.append(self._ui_heatmap_mode_selector)
 
     def _update_ui_custom(self):
         pass
@@ -560,4 +560,5 @@ def deinit_ui(self):
         self.remove_menu()
 
     def cleanup(self):
+        self._ui_heatmap_mode_selector = None
         self.save_surface_definitions_to_file()
diff --git a/pupil_src/shared_modules/surface_tracker/surface_tracker_offline.py b/pupil_src/shared_modules/surface_tracker/surface_tracker_offline.py
index ad89f0e050..4b4d90b9bf 100644
--- a/pupil_src/shared_modules/surface_tracker/surface_tracker_offline.py
+++ b/pupil_src/shared_modules/surface_tracker/surface_tracker_offline.py
@@ -340,7 +340,11 @@ def _update_surface_heatmaps(self):
             surf_idx = self.surfaces.index(surface)
             gaze_on_surf = self.gaze_on_surf_buffer[surf_idx]
             gaze_on_surf = itertools.chain.from_iterable(gaze_on_surf)
-            gaze_on_surf = (g for g in gaze_on_surf if g["confidence"] >= self.g_pool.min_data_confidence)
+            gaze_on_surf = (
+                g
+                for g in gaze_on_surf
+                if g["confidence"] >= self.g_pool.min_data_confidence
+            )
             gaze_on_surf = list(gaze_on_surf)
             surface.update_heatmap(gaze_on_surf)
 
diff --git a/pupil_src/shared_modules/surface_tracker/surface_tracker_online.py b/pupil_src/shared_modules/surface_tracker/surface_tracker_online.py
index ea94fb3b9c..85335c8c73 100644
--- a/pupil_src/shared_modules/surface_tracker/surface_tracker_online.py
+++ b/pupil_src/shared_modules/surface_tracker/surface_tracker_online.py
@@ -61,7 +61,7 @@ def ui_info_text(self):
 
     @property
     def supported_heatmap_modes(self):
-        return [Heatmap_Mode.WITHIN_SURFACE, Heatmap_Mode.ACROSS_SURFACES]
+        return [Heatmap_Mode.WITHIN_SURFACE]
 
     def _update_ui_custom(self):
         def set_freeze_scene(val):
@@ -95,6 +95,8 @@ def set_gaze_hist_len(val):
         )
 
     def recent_events(self, events):
+        if self._ui_heatmap_mode_selector is not None:
+            self._ui_heatmap_mode_selector.read_only = True
         if self.freeze_scene:
             # If frozen, we overwrite the frame event with the last frame we have saved
             current_frame = events.get("frame")
@@ -132,7 +134,11 @@ def _update_surface_corners(self):
     def _update_surface_heatmaps(self):
         for surface in self.surfaces:
             gaze_on_surf = surface.gaze_history
-            gaze_on_surf = (g for g in gaze_on_surf if g["confidence"] >= self.g_pool.min_data_confidence)
+            gaze_on_surf = (
+                g
+                for g in gaze_on_surf
+                if g["confidence"] >= self.g_pool.min_data_confidence
+            )
             gaze_on_surf = list(gaze_on_surf)
             surface.update_heatmap(gaze_on_surf)
 
diff --git a/pupil_src/shared_modules/system_graphs.py b/pupil_src/shared_modules/system_graphs.py
index 8f0be5b9ec..955deb99c8 100644
--- a/pupil_src/shared_modules/system_graphs.py
+++ b/pupil_src/shared_modules/system_graphs.py
@@ -117,10 +117,10 @@ def recent_events(self, events):
         if "frame" not in events or self.idx != events["frame"].index:
             for p in events["pupil"]:
                 if p["topic"] == "pupil.0.2d":
-                    assert p["id"] == 0 #sanity check
+                    assert p["id"] == 0  # sanity check
                     self.conf0_graph.add(p["confidence"])
                 if p["topic"] == "pupil.1.2d":
-                    assert p["id"] == 1 #sanity check
+                    assert p["id"] == 1  # sanity check
                     self.conf1_graph.add(p["confidence"])
 
         # update wprld fps graph
diff --git a/pupil_src/shared_modules/tasklib/manager.py b/pupil_src/shared_modules/tasklib/manager.py
index b1cebf67aa..1252961f9d 100644
--- a/pupil_src/shared_modules/tasklib/manager.py
+++ b/pupil_src/shared_modules/tasklib/manager.py
@@ -10,6 +10,9 @@
 """
 
 import tasklib.background
+import logging
+
+logger = logging.getLogger(__name__)
 
 
 class PluginTaskManager:
@@ -28,8 +31,7 @@ class PluginTaskManager:
     """
 
     def __init__(self, plugin):
-        self._recently_added_tasks = []
-        self._running_tasks = []
+        self._tasks = []
         plugin.add_observer("recent_events", self.on_recent_events)
         plugin.add_observer("cleanup", self.on_cleanup)
 
@@ -84,7 +86,7 @@ def create_background_task(
             kwargs,
             patches,
         )
-        self._recently_added_tasks.append(task)
+        self._tasks.append(task)
         return task
 
     def add_task(self, task):
@@ -95,36 +97,46 @@ def add_task(self, task):
         Similarly to create_task(), you don't need to start the task before adding
         it, but you can if you want.
         """
-        self._recently_added_tasks.append(task)
+        self._tasks.append(task)
 
     def on_recent_events(self, _):
-        self._start_recently_added_tasks()
-        self._update_running_tasks()
-
-    def on_cleanup(self):
-        self._kill_all_running_tasks()
-        self._recently_added_tasks = []
-        self._running_tasks = []
-
-    def _start_recently_added_tasks(self):
-        for task in self._recently_added_tasks:
-            # we test because the user might have already started it manually
+        for task in self._tasks.copy():
             if not task.started:
                 task.start()
-            self._recently_added_tasks.remove(task)
-            self._running_tasks.append(task)
-
-    def _update_running_tasks(self):
-        for task in self._running_tasks:
-            if task.ended:
-                self._running_tasks.remove(task)
-            else:
+            if task.running:
                 task.update()
+            if task.ended:
+                self._tasks.remove(task)
+
+    def on_cleanup(self):
+        self._kill_all_running_tasks()
+        self._tasks = []
 
     def _kill_all_running_tasks(self, grace_period_per_task=None):
-        for task in self._running_tasks:
-            # the test is for tasks that terminate between the last update and this
-            # method call, i.e. for tasks that had no chance to get removed from
-            # self._running_tasks
+        for task in self._tasks:
             if task.running:
                 task.kill(grace_period=grace_period_per_task)
+
+
+class UniqueTaskManager(PluginTaskManager):
+    """TaskManager ensuring tasks are unique by identifier"""
+
+    def add_task(self, task_new, identifier: str):
+        UniqueTaskManager._patch_task(task_new, identifier)
+        task_duplicated = self._get_duplicated_task(identifier)
+        if task_duplicated is not None:
+            state = "running" if task_duplicated.running else "queued"
+            logger.debug(f"Replacing {state} task with ID '{identifier}'")
+            if task_duplicated.running:
+                task_duplicated.kill(grace_period=None)
+            self._tasks.remove(task_duplicated)
+        super().add_task(task_new)
+
+    def _get_duplicated_task(self, identifier):
+        for task_prev in self._tasks:
+            if task_prev._unique_task_identifier == identifier:
+                return task_prev
+
+    @staticmethod
+    def _patch_task(task, identifier: str):
+        task._unique_task_identifier = identifier
diff --git a/pupil_src/shared_modules/video_overlay/controllers/overlay_manager.py b/pupil_src/shared_modules/video_overlay/controllers/overlay_manager.py
index d3342b05c9..1ef8cee597 100644
--- a/pupil_src/shared_modules/video_overlay/controllers/overlay_manager.py
+++ b/pupil_src/shared_modules/video_overlay/controllers/overlay_manager.py
@@ -16,11 +16,10 @@
 
 
 class OverlayManager(SingleFileStorage):
-    def __init__(self, rec_dir, plugin):
-        super().__init__(rec_dir, plugin)
+    def __init__(self, rec_dir):
+        super().__init__(rec_dir)
         self._overlays = []
         self._load_from_disk()
-        self._patch_on_cleanup(plugin)
 
     @property
     def _storage_file_name(self):
@@ -54,12 +53,3 @@ def most_recent(self):
     def remove_overlay(self, overlay):
         self._overlays.remove(overlay)
         self.save_to_disk()
-
-    def _patch_on_cleanup(self, plugin):
-        """Patches cleanup observer to trigger on get_init_dict().
-
-        Save current settings to disk on get_init_dict() instead of cleanup().
-        This ensures that the World Video Exporter loads the most recent settings.
-        """
-        plugin.remove_observer("cleanup", self._on_cleanup)
-        plugin.add_observer("get_init_dict", self._on_cleanup)
diff --git a/pupil_src/shared_modules/video_overlay/plugins/generic_overlay.py b/pupil_src/shared_modules/video_overlay/plugins/generic_overlay.py
index d3e3c5a8e3..709a1234d8 100644
--- a/pupil_src/shared_modules/video_overlay/plugins/generic_overlay.py
+++ b/pupil_src/shared_modules/video_overlay/plugins/generic_overlay.py
@@ -27,7 +27,13 @@ class Video_Overlay(Observable, Plugin):
 
     def __init__(self, g_pool):
         super().__init__(g_pool)
-        self.manager = OverlayManager(g_pool.rec_dir, self)
+        self.manager = OverlayManager(g_pool.rec_dir)
+
+    def get_init_dict(self):
+        # Save current settings to disk, ensures that the World Video Exporter
+        # loads the most recent settings.
+        self.manager.save_to_disk()
+        return super().get_init_dict()
 
     def recent_events(self, events):
         if "frame" in events:
diff --git a/pupil_src/shared_modules/video_overlay/utils/image_manipulation.py b/pupil_src/shared_modules/video_overlay/utils/image_manipulation.py
index 9696551015..9403611db2 100644
--- a/pupil_src/shared_modules/video_overlay/utils/image_manipulation.py
+++ b/pupil_src/shared_modules/video_overlay/utils/image_manipulation.py
@@ -10,10 +10,13 @@
 """
 
 import abc
+import logging
 
 import cv2
 import numpy as np
 
+logger = logging.getLogger(__name__)
+
 
 class ImageManipulator(metaclass=abc.ABCMeta):
     @abc.abstractmethod
@@ -73,6 +76,12 @@ def render_pupil_3d(self, image, pupil_position):
         conf = int(pupil_position["confidence"] * 255)
         self.render_ellipse(image, el, color=(0, 0, 255, conf))
 
+        if pupil_position["model_confidence"] <= 0.0:
+            # NOTE: if 'model_confidence' == 0, some values of the 'projected_sphere'
+            # might be 'nan', which will cause cv2.ellipse to crash.
+            # TODO: Fix in detectors.
+            return
+
         eye_ball = pupil_position.get("projected_sphere", None)
         if eye_ball is not None:
             try:
@@ -86,10 +95,15 @@ def render_pupil_3d(self, image, pupil_position):
                     color=(26, 230, 0, 255 * pupil_position["model_confidence"]),
                     thickness=2,
                 )
-            except ValueError:
-                # Happens when converting 'nan' to int
-                # TODO: Investigate why results are sometimes 'nan'
-                pass
+            except Exception as e:
+                # Known issues:
+                #   - There are reports of negative eye_ball axes, raising cv2.error.
+                #     TODO: Investigate cause in detectors.
+                logger.debug(
+                    "Error rendering 3D eye-ball outline! Skipping...\n"
+                    f"eye_ball: {eye_ball}\n"
+                    f"{type(e)}: {e}"
+                )
 
     def render_ellipse(self, image, ellipse, color):
         outline = self.get_ellipse_points(
diff --git a/pupil_src/shared_modules/vis_watermark.py b/pupil_src/shared_modules/vis_watermark.py
index d679bc69c8..952faff2e6 100644
--- a/pupil_src/shared_modules/vis_watermark.py
+++ b/pupil_src/shared_modules/vis_watermark.py
@@ -35,7 +35,7 @@ def __init__(self, g_pool, selected_watermark_path=None, pos=(20, 20)):
         self.menu = None
 
         available_files = glob(
-            os.path.join(self.g_pool.user_dir, "*png")
+            os.path.join(self.g_pool.user_dir, "[!.]*png")
         )  # we only look for png's
         self.available_files = [
             f for f in available_files if cv2.imread(f, -1).shape[2] == 4