This is how I did it, after I put all of my music in jellyfin without thinking. At the end there was one or two artists/albums I couldn’t get to convert properly.

Did you try also deleting all of the old metadata, to try to get it back to a clean slate

I had this exact same issue and many other odd things. The best advice I can give that worked for me was to one by one take each album off my server pass it through music brains (this looks for and edits metadata) and then place it back into Jellyfin.

It was well worth it in the end. I couldn’t get Jellyfins metadata to work reliably for me, but this was the only issue I have had and the good Jellyfin provides once you have it ‘cleaned’ up is fantastic.