I found a curious behaviour yesterday. I copied as root a system file to a floder in my user’s account managed by syncthing. The file was not synced. I assumed it was due to the permissions and ownership of the file, so I changed them to my user. Nevertheless, the file was not synced. It seems the system didn’t notice the change. When I moved the file to another folder it was immediately recognized and synced.
My versions are syncthing 0.14.46+ds1-1 talking to 0.14.43
and syncthing-inotify 0.8.7 (on both)
Probably s-inotify tried to get it index when it appeared, that failed due to permissions. Due to running with inotify there wouldn’t be very frequent periodic scans so your permission fix wouldn’t get picked up swiftly. Permission/owner-only changes don’t cause any inotify events, I think.
I am not sure about owner changes in general, neither about syncthing-inotify, but the “new integrated” inotify based watcher does catch permission changes.