Exactly two artists.
I did some work with the "Tag Explorer" for a couple of tracks that were full of "Tag Spam" and for them, kept entries like the one below, because I do not know what the "WXXX" tag does.
1) is there a reference of MP3 tags somewhere?
2) Might that be related to the problem?
3) Should I remove these tags?
Funnily Enough, the album has 21 tracks, so it's already quite a lot of these "empty artists" if true.