I was trying to use the right artist credits on http://ngs.musicbrainz.org/release/3747cbaf-1f66-4b20-87b8-93afc7c00651
That implied changing the release artist (credit), and then changing several track artist (credits). If I select "change track artists" while changing the release artist (as track 1 is by him) it makes me unable to edit the rest of the track credits at all (any changes I make there are lost). Changing release artist there and track artist on the tracklist (not checking "change track artists") works fine though.