There’s definitely a bug of some sort. I reported it here:
It’s easy to reproduce. Add an album that can’t be matched at MusicBrainz. Then add the album to the Musicbrainz database. Wait a few days for Plex to sync the data from their database… Match or Fix Match will bring up the proper album, but refuses to match.
A workaround till the bug is fixed is to “Refresh Metadata” for the artist. For some reason that will match the album properly.
