There seems to be an issue with iCloud sync. After I have watched a movie or episode it is correctly marked as watched. However if I rename the file or move it to a different folder, it seems to think it is a totally new file and marks it as unwatched…even though it has been watched.
This behavior did not occur when trakt was used for syncing. This becomes annoying after a while because I cannot rely on iCloud sync alone to keep track of watched files.