Save in iOS or iPadOS 26.2 in Numbers or other Apps often hangs

When I change a NextCloud file in Numbers, Keynote or other iOS Apps it often hangs while saving.

I see the file in the recent opened files incl. a dotted cloud symbol and a 95% progress cycle. When I tip on it nothing happens. When I leave the app and reload the file after some time, all changes are lost and I get only the old file without my changes. With this behaviour, NextCloud is not productive usable for me.

Btw. when I store e.g. downloads directly to NextCloud App (e.g. via share button in Safari) it works as expected, only working with iOS Apps on files stored in NextCloud (open, change, save) is not reliable. Same today after creating a file in Keynote locally on iPad and used the Move function of Keynote via log press on the local file and select NextCloud as destination.

Does anyone have an idea if I can do something to improve the situation?

NextCloud App in iPadOS 7.2.2.4 and Server 31.0.10 (Hezner)

Thank you very much!!

Christian