File Sync local to cloud will not work

Nextcloud version:
Operating system and version: NextCloudePi v1.51.1 / Debian GNU/Linux 11. 5.15.61-v8+ (aarch64)
Apache or nginx version: no idea
PHP version: 8.1.17
Client used with Ubuntu: Version 3.4.2, ubuntu-5.19.0-38-generic
Client OS: Ubuntu 22.04.2 LTS

Despite the NextCloudPi freshly installed several times, the synchronization of the files is faulty for me. The synchronization from the Raspi (files I upload to the web interface) seems to work fine, but in the opposite direction (the data stored from the local side) does not sync with the cloud.

I have been using the NextCloudPi for many years and rarely had any problems. But right now I’m pretty desperate!

Thank you very much for your help!

Is this the first time you’ve seen this error? Yes

These Errors I found. Maybe it helps:
Error webdav Sabre\DAV\Exception: Unknown error while seeking content
Error no app in context Sabre\DAV\Exception\BadRequest: Expected filesize of 1745921 bytes but read (from Nextcloud client) and wrote (to Nextcloud storage) 8192 bytes. Could either be a network problem on the sending side or a problem writing to the storage on the server side.
Error PHP Error: fread(): Unable to create temporary file, Check permissions in temporary files directory. at /var/www/nextcloud/3rdparty/icewind/streams/src/Wrapper.php#55
Error PHP Error: fread(): file created in the system’s temporary directory at /var/www/nextcloud/3rdparty/icewind/streams/src/Wrapper.php#55

Update2: Maybe similar to this issue: [Bug]: Client not syncing when empty TAGS file is in folder · Issue #5605 · nextcloud/desktop · GitHub