I just removed my Music library and re-created it, since the new music agent can’t handle most Various Artists compilations (i.e. Danish). So I made a Music (with known artists) and a separate Music \ VA library for various artists.
This did actually solve the matching of Guns N' Roses, since this isn’t handled manually trough the artist match picker. So this must almost be a PlexWeb problem or a agent upgrade (the new menu option on the library) bug of some sorts (I guess).
(Yes, I know. I could add the missing compilations to Musicbrainz manually)
