Thanks for the screenshot and doing a plex dance.
From what you showed, it looks like naming, tagging, and library setup issues with a well known album. For reference, the Plex Support Articles are the user manual, like these:
Music Files Naming and Organizing
Adding Music Media From Folders
I’ll try to summarize what I do to avoid your problems
In the music library 3 dots Manage Library → Edit … → Advanced
- music library Scanner = Plex Music
- music library Agent = Plex Music
- prefer local metadata = unchecked
- genres = Plex Music
- album art = Both Plex Music and Local Files
Using Musicbrainz Picard I match the album and let it write all the tags, which is the primary thing Plex will use to match the artist, album, tracks.
Following the Plex Naming Conventions for Music in the second link above, I would name the files and folders like this starting with your base folders. (these are used as a fallback to the tags)
/volume1/music/Music/
Michael Jackson/
HIStory Past, Present and Future, Book I/
101 - Billie Jean.flac
102 - The Way You Make Me Feel.flac
103 - Black or White.flac
...
114 - Wanna Be Startin' Something.flac
115 - Heal the World.flac
201 - Scream.flac
202 - They Don't Care About Us.flac
203 - Stranger in Moscow.flac
204 - This Time Around.flac
205 - Earth Song.flac
206 - D.S..flac
207 - Money.flac
208 - Come Together.flac
209 - You Are Not Alone.flac
210 - Childhood.flac
...
213 - Smile.flac
Failure to write the filenames to include the disc number like I did can hurt your matching, and failure to tag the files themselves with disc numbers will also.
