Not all images are transferred


I have noticed several times now that not all selected photos of mine are transferred to Nextcloud (Wifi).

I select 10 photos in my gallery, press share, select the folder in my Nextcloud and confirm.

Most of the time I have to check the photos again to make sure that all of them have been uploaded. What could be the reason for this? Thanks

OnePlus Nord - Android 11
Nextcloud Android 3.17.1
Nextcloud 22.2.0 (Hetzner)

Problem is somehow related to my old thread: Problems with identical files in the taskbar

Apparently 10 out of 10 photos are uploaded after all. But not all of them are visible in the Windows Explorer of Nextcloud. Since they are not visible, I have triggered a new upload in which Nextcloud asks me which file I want to keep. Here it comes to sync errors.

No idea what exactly is the problem here.