File content lost in offline mode when using microsoft word app. Potential reason: Files App does not allow access to offline synced nextcloud folders. Debugging help needed!

Expected behaviour

File content is stored on ipad and synced with nextcloud after wifi connection recovery.

Actual behaviour

File content written in offline mode was completely lost and file was resetted to old content.
I think...but i have no really facts that support my thesis: In Files App i can not open the offline synced folder from nextcloud storage. This is reproducable when turning wifi off AND activating flight mode. Activate flight mode only did not cause this issue: i was able to open the folder.
Open files & folder in nextcloud app was working!

The detailled reason is not really clear. And...it was only one time reproducable and i am not 100% sure that i describe everything correct.
Thats why i need help with this issue, maybe someone has some more idea to reproduce this or find some logs or maybe a shadow copy of the file change. And it was also not myself who lost the data on his ipad (i'm also an apple newbie)

Steps to reproduce

• got new ipad pro

• Installed Nextcloud app a week ago and synced ~20GB of data with the option "offline available favourites"

• installed Word, Outlook, Teams etc and activated product with company license (onedrive and sharepoint storage is enabled, but not used)

• Created a new word document in Word, add some lines of text and save with "save", then select the "Files App", then nextcloud, the folder of choice and chnage the filename. Then press the button "move". Wifi was enabled and the file was synced to nextcloud server. Swipe back to "desktop" and close ipad. Autosave was enabled in Word

• Next day, open ipad withour wifi or mobile connectivity. Open Word. Add some other text (4 hours, was a lot of text)

• Former Windows User: Try to save and press in menu bar the "left arrow" to open the menu with file history, open file etc.

• the file history did NOT show the current edited file

• user did nothing else, closed ipad cover

• user went home, opened ipad (with wifi connectivity) and asked my "my file is gone". I know....not really a good error message

• me opened files app, searched the file and opened it. Content was same content then in the evening before. All text created was not there.

• Checked Nextcloud synclog. The file with the issue was synced in the same time i

Then: played around much and figured out:

• Open documents from word, from files app etc, save documents, edit, close (and really close) word app, etc all with some new created files in nextcloud folders
• Try to test every action in online and /or offline mode
  Results:
• found 2 or 3 times word crashing (try to open and closed after that)
• Now the nextcloud issue i think i found: In Files App i can not open the offline synced folder from nextcloud storage. This is reproducable when turning wifi off. Activate flight mode only did not cause this issue: i was able to open the folder.
  Open files & folder in nextcloud app was working!
• 1 time i got same issue: new docx, edit text, switch to flight mode, edit again, open same docx from files app and got the old content. But i didn't find a reason the reproduce this again.

Sorry for the much details, but i am not sure what is really important to trace this issue. Maybe someone has an idea (grab a hidden log file, app crash protocol, whatever.) I don't know much about iOS troubleshooting.

Reasoning or why should it be changed/implemented?

Annoying User won't work with her new ipad until this is fixed.

iOS version

13.6

App version

3.0.4.11

Server configuration

Operating system:
Debian Linux 10.5
Web server:
Apache 2.4.38 (builtin)
Database:
mysqld 10.3.23-MariaDB-0+deb10u1
PHP version:
7.4
Nextcloud version: (see Nextcloud admin page)
19.01

The issue names no source files or tests. Start by reproducing the failure on an iPad running iOS 13.6 with Nextcloud 3.0.4.11, Microsoft Word, the Files app, and an offline-synced folder, while checking the Nextcloud sync log. Done means the trigger is identified and offline edits are preserved or the limitation is documented.