first I thought it was an issue of the android wrapper: https://github.com/Catfriend1/syncthing-android/issues/734
now I’m not so sure. the problem files are all created with “curl … -o file.mp3” and regardless of what I do after ST saw them they cause the issue. if I -o the files elsewhere and rsync them into the ST shared folder, it seems to work fine. not sure in which direction to think next.