Plex will not recognize new movies added to library

The last few months it will not recognize any new movie files added. All are mp4. If I unlink the movie folder and relink to the folder it will recognize it then. Is there a new update that could have messed with this?

Nothing comes to mind except maybe if you are running on a Synology due to some permissions changes. Plex Media Server security changes for Synology users

Have you looked at the scanner log?