Problem making mock-up project without mp3

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Describe the bug
Had an error putting in the txt files for annotation, so tried creating other Item Manifests and continuing to get error codes. At first, it was from line 123 for both the error after entering the annotation and the second Item Manifest, but the last attempt said it was from line 133.
To Reproduce
Steps to reproduce the behavior:

1. Input manifest information with placeholder link
2. Put in the txt file with annotations
3. Get error code from that
4. Getting error code from putting in other annotations or new item manifests

Expected behavior
I would desire the manifest to build and not receive error page

Screenshots
Please add screenshots to help explain your problem.

Additional context
Here is the txt file that was used for the first annotation that gave us the first error:
SPA_19810520_B (1).txt

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Resolved, it ultimately built

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Actually, there might still be a problem: but it still may just have to deal with the steps above:
but to add:
For the annotations page titled "Radio Venceremos" that has the recording (the placeholder), I cannot edit the page, even to delete it. When clicking on:

the "radio-venceremos.md" to edit it and attempt to delete it, it leads me to this error page: