http://musicbrainz.org/release-group/bae7c6ed-0c4e-4442-903d-18fd22dbe848/edits

http://musicbrainz.org/edit/22895150 - first release's art
http://musicbrainz.org/edit/22895158 - second release's art
http://musicbrainz.org/edit/22895180 - third release's art

If you look at the release group now, the art is the third image:
http://musicbrainz.org/release-group/bae7c6ed-0c4e-4442-903d-18fd22dbe848

I am now trying to change it to the first image in http://musicbrainz.org/edit/22895207 , which is not an auto-edit.

Two suggestions:
1) If the release group image was not set manually, then editing it should be an auto-edit.
2) "Set cover art" edit types should probably display the previous image, not just the new image.