Using Plex libraries, if you start watching a movie in Infuse, stop it (for example at 50%) and you finish watching it in Plex player, in Plex is marked as watched, but in Infuse it’s still at 50%, never changes to watched in Infuse. There no problem if you watch a full movie in Plex player. Watch status sync only fails if you start watching in Infuse and you finish in Plex player.
I also noticed when I finish watching a movie in one Apple TV in Infuse, it marks as watched in Plex and in that Infuse Apple TV. I have two more Apple TV with Infuse where that movie is marked as unwatched even I force sync with Plex. In other Plex clients, movie is marked as watched.
I don’t use icloud sync and trakt in Infuse. I expect to retrieve all information from the server.