Verify that you’re not affected: Library.db size more than doubled in latest version
Also, if you recently changed servers or a Plex friend of yours deleted/switched theirs, it’s probably worth going over the full list of servers.
Remove deleted servers of yours here: https://app.plex.tv/desktop/#!/settings/devices/pms
(Crareful to delete only unused ones!)
Defunct servers of Plex friends can be left here: https://app.plex.tv/desktop/#!/settings/manage-library-access