After editing a release (converting featuring credit from track to artists), the two involved tracks doesn't seem to have any artists associated, ditto for the linked recordings:

• http://musicbrainz.org/release/04ea8c9d-71af-40f0-a647-067f2e80717f (tracks 5 & 7)
• http://musicbrainz.org/recording/0a35520e-4deb-479f-845f-27947e2ba9e9
• http://musicbrainz.org/recording/8e3be8bb-349a-4892-81d2-584cb61d6e49

I've tried to edit the release again to fix it, but it has not changed anything.