Nextcloud Android App does not synchronize proper

I have a crazy problem with synchronizing a folder on my Android Tablet.
On Server side I use:
Nextcloud Hub 9 30.0.4
Based on Linux
On Android side:
Android-Version 14 (the latest one distributed by Samsung) and the current Nextcloud client.

Basic information - I use the same constellation on my Andord Phone. There the synchronization of exactly this folder works perfect.

On Tablet side the synchronization basically also works. Only the special folder I need doesn’t. I also deleted the NextCloud client and the data path it used and reinstalled again. Synchronization doesn’t work.
I assume, that there is some information stored about the folder, which says the client that it is already synchronized.
If I start the synchronization the synchronization sign (blue circle with double arrow) is displayed only for a short moment. For the first synchronization it should be displaed longer.

So my question - is there a log or some detailled information where the reason can be figured out, why it doesn’t work. Or can the configuration be deleted after deleting the client?