Restoring chat backup loads forever

[fnetX]

Bug Description

I wanted to set up FluffyChat and gain access to previous messages using my chat backup. I know that the key worked fine in other clients recently. However, when using it in FluffyChat, it results in an endless loading spinner "Loading... Please wait."

Steps to Reproduce

1. Enable chat backup
2. Enter recovery key
3. Press "Unlock"
4. See an endless loading spinner and no network or high CPU activity

Expected Behavior

After loading for a while, the process is completed.

App Version

1.23 (F-Droid)

Additional Platform Information

Lenovo TB2-X30F (rather old device), Android 6

Additional Context

Spotted this in logcat

01-20 02:33:27.195 28565 28580 I flutter : [Matrix] Unable to self sign with recovery key after successfully open existing SSSS - Exception: Master pubkey key doesn't match
01-20 02:33:27.195 28565 28580 I flutter : #0      CrossSigning.selfSign (package:matrix/encryption/cross_signing.dart:111)
01-20 02:33:27.195 28565 28580 I flutter : <asynchronous suspension>
01-20 02:33:27.195 28565 28580 I flutter : #1      BootstrapDialogState.build.<anonymous closure> (package:fluffychat/pages/bootstrap/bootstrap_dialog.dart:306)
01-20 02:33:27.195 28565 28580 I flutter : <asynchronous suspension>
01-20 02:33:27.195 28565 28580 I flutter : 
01-20 02:33:27.232  1498  1498 I Keyboard.Facilitator: onStartInput()
~~~