I have two audio files that Plex insists on merging into one. It is only doing this with one book in the series. (new narrator in the new release)
File 1: \media\audiobooks\Robert Jordan\Wheel of Time\1990 - The Great Hunt [Wheel of Time 2]\The Great Hunt (1990) [Wheel of Time 2].m4b
File 2: \media\audiobooks\Robert Jordan\The Wheel of Time\2022 - The Great Hunt [The Wheel of Time 2]\The Great Hunt (2022) [The Wheel of Time 2].m4b
As you can see only The Great Hunt merged the items. the other books remained separate. there is not option to split as it there was an accidental merge. I did the Plex dance and they just keep merging.
Plex doesn’t have a dedicated naming schema for audio books. The best you can currently do is to use the organization and naming used for regular music.
In your case, your naming isn’t strictly following that – so it appears Plex is considering both tracks (books) to be part of the same album (book?).
media
audiobooks <- I guess your library is pointing to this folder?
Robert Jordan
Wheel of Time
1990 - The Great Hung [Wheel of Time 2]
The Great Hunt (1990) [Wheel of Time 2].m4b
The Wheel of Time
2022 - The Great Hunt [The Wheel of Time 2]
The Great Hunt (2022) [The Wheel of Time 2].m4b
Or your files might have conflicting embedded metadata?