Problem with the offline function, which works very, very slowly or not at all

Expected behaviour

I suspect that there is a problem with the offline function in the iOS app in both direction.

Actual behaviour

The data is displayed quickly and can also be viewed. Only when I turn on the offline function, the synch no longer works properly. That is, after 2-3 files the iPhone crashes and from then on nothing happens. The display to the right of the file rotates, but does not happen. This state can last several hours before some data is synchronized again. If you want to load e.g. 8 pictures (each about 3MB) from the iPhone to the server, only about 3-4 pictures go very fast and from then on again the behavior described before. The remaining pictures are uploaded only after days or not at all.
I suspect that there is a problem with the offline function in the iOS app.

Server configuration

Web server: Synology NAS ds124 with actual DSM

**Database:**Apache HTTP Server 2.4

**PHP version:**7.4

**ownCloud version:**10.13.1

Storage backend (external storage):

Client

**iOS version:**17.0.3

**ownCloud app version:**12.0.3 build 282

**Device model:**SE 2022

Logs

Sorry, since it is a corporate device, I am not allowed to distribute log files. I hope you can still help.