We now are onto a lead.
For those with the problem still, who have not reverted to an earlier version,
- Stop PMS
- Delete
"/var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Plug-in Support/Data/com.plexapp.system/HTTPCookies" - Start PMS
- Scan files - see if it rectifies itself
- If not - Refresh the metadata
- Report results and whether Scan or Refresh needed.