This appears to have started with this version? When I updated, it start the behavior of a condition like, for example, Swan Lake. There are multiple CDs in that album, the tracks for Disk 1 and Disk 2 are mashed together. For example, track 1 on Disk 1 appears in Disk 2 instead. Disk 2 has both track 1s.
Is your library configured to prefer embedded metadata? If so, make sure the Discnumber tag is properly populated (not blank, and “1, 2, 3” or “01, 02, 03,” not “1/5, 2/5, 3/5”). Assuming the rest of the tags that Plex reads are properly populated, if the discnumber isn’t correct, Plex can have this particular problem.