You can try restoring a database backup that predates the changes.
See FAQ 30 - DSM 7 - Database Repair using a Backup copy.
Then rescan your libraries.
You may have problems with posters. The Internet Archive (archive.org) is offline due to DDOS attacks. Plex will not be able to retrieve posters for some media.
From Plex Media Server.2.log:
Oct 10, 2024 13:35:58.581 [140372717218616] DEBUG - [HCl#37ae5] HTTP requesting GET https://ia800205.us.archive.org/3/items/mbid-f9a7c00b-f5e3-4090-9829-b32f9b86ca2c/mbid-f9a7c00b-f5e3-4090-9829-b32f9b86ca2c-12697728653.png
Oct 10, 2024 13:36:13.597 [140372601252664] DEBUG - [HttpClient/HCl#37ae5] HTTP simulating 408 after curl timeout
Oct 10, 2024 13:36:13.597 [140372717218616] ERROR - MetadataAgent: unable to save posters asset from 'https://ia800205.us.archive.org/3/items/mbid-f9a7c00b-f5e3-4090-9829-b32f9b86ca2c/mbid-f9a7c00b-f5e3-4090-9829-b32f9b86ca2c-12697728653.png' to '"/var/packages/PlexMediaServer/shares/PlexMediaServer/AppData/Plex Media Server/Metadata/Albums/1/9162ef58817af64df4b7adb502d7c5561dad9cd.bundle/Contents/_combined/posters"'
