Shared Nextcloud Office files not saved after other user edits within app (web okay)

Steps to reproduce

1. Create Nextcloud Office document/spreadsheet/presentation file
2. Share file with other user on server, granting rw and re-sharing rights
3. Other user opens and edits the file from within the Nextcloud iOS app, and saves it
4. Open the file and observe that the changes made by the other user haven't been saved/aren't there

Expected behaviour

That changes made by the other user, just like for the owner, are saved.

It works fine if edited via the browser, both on the phone and on a PC, it only fails (silently doesn't save) when opening and editing from within the iOS app.

Actual behaviour

Changes made by other user from iOS app is not saved. If doing it from a browser, e.g. Safari, it works.

Logs

I will add my logs in the comments.

Environment data

iOS version: 17.2.1

Nextcloud iOS app version: 4.9.6.1

Server operating system: Ubuntu Server 22.04

Web server: Apache 2.4.52-1ubuntu4.7

Database: MySQL 8.0.35-0ubuntu0.22.04.1

PHP version: 8.1.2-1ubuntu2.14

Nextcloud version: 27.1.5

Docker image collabora/code: 23.05.6.4

Start by reproducing the failure in the Nextcloud iOS app with a shared Nextcloud Office file, then compare it with editing through Safari. Review the logs mentioned in the issue and trace the save behavior for edits made by a non-owner. Done means the other user's edits persist when the file is opened and edited in the iOS app.