For example, see

Merge artist: http://musicbrainz.org/edit/14475428

Release group artist credits are incorrect: http://musicbrainz.org/artist/749efdb9-ff98-4a3f-a0f1-5cdaaca244c6
as are recording artist credits http://musicbrainz.org/recording/17bab9c2-4684-4bd8-be05-7045cadf762d

I also note that the MBIDs for the artist credit are the OLD MBIDs prior to merge. I believe these should not be visible anywhere on the website after such an artist merge; only maintained in the DB for permalink redirecting purposes?

I saw the same thing myself on test yesterday as well:

Merge artist: http://test.musicbrainz.org/edit/14459950
Old artist credits on release: http://test.musicbrainz.org/release/8d6b50e0-d1de-4f93-a9d7-46b2703e565f

Same issue with old MBIDs lingering.