Changes made in one editor not visible in another client

[max-nextcloud]

Describe the bug
During editing sessions with multiple parties the views get out of sync.
Changes made in one editor are not reflected anymore in another editor.
The other way round changes are still applied

To Reproduce
Hard to reproduce.

1. Start an editing session with multiple people - ideally with an old file
2. Screenshare one editor state
3. Everyone makes changes
4. Check if the result is in sync with the screenshare for everyone
5. Find that changes in one editor are not reflected in some other editor.

Expected behavior
Smooth synchronization between all parties that join the editing session.

Screenshots
Will add later.

Server details:
cloud.nextcloud.com on 30.0.3RC1

Client details:
multiple different browsers across different network connections

[max-nextcloud]

We tried to reproduce this on various occasions. With the latest update we were only able to reproduce it once with the latest code version. What was special about that one time:

• Long editing session (team meeting)
• existing document with a long editing history
• no force reload before starting to edit but some people had the editor component opened before (debugYjs failed for them).
• pendingStructs showed in the yjs state.

[max-nextcloud]

We tried to reproduce this several time during our meetings but failed thus far. Looks like the one time we still saw might have been a left over of the long running session.