Syncthing hiding files on Truenas Scale SMB shares

Yes I have added a Testfolder in the syncthing app. The folder is created, I shared it with my client pc. The folder appears. I added a file in the testfolder, the file does not appear and I get an out-of-sync error.

Interesting: this testfolder is owned by apps. All the other folders on my Photo dataset are owned by user koen (me). Some of the subfolders in 2025 seem to be onwned by me, but also user 3003.