Plex - Bug with images not displaying

I've had an ongoing bug with Plex where the images were not being displayed even where they were visible in the fix match checks. Going on from that the collections quad split was also not being populated. A post on reddit provided some assistance although simply redownloading the metadata did not repopulate the images. Although I perhaps have to wait and see.

 The issue is that in your DB there is a mismatching entry. I solved this issue but clearing out the data:
    Stop Plex: sudo systemctl stop plexmediaserver.service
    login to plex SQL lite: '/usr/lib/plexmediaserver/Plex SQLite' /var/lib/plexmediaserver/Library/Application Support/Plex Media Server/Plug-in Support/Databases/com.plexapp.plugins.library.db
    Run this SQL: update metadata_items set user_thumb_url = "" where user_thumb_url != "";
    Start Plex: sudo systemctl start plexmediaserver.service
    Navigatie to Plex - > click on the 3 dots in front of the named Library -> Manage Library -> Refresh All MetaData.

Using Fix Match is currently working to update a single album or film, but the quad splits may need further work. I've had mixed success on recreating the collection poster, with the Beatles working fine, but Pirates of the Caribbean did not. Still work in progress. The other problem is managing classical albums where the 'artist' and 'composer' are equally useful, but Plex makes a mess of adding CD's a single albums where there are a combination of either on the disk. Something I am hoping I may be able to address in nextcloud!