It seems to happen when the medium has a disc ID. All the ones I've checked so far where it's happened have had disc IDs, so I tried editing a random release with a disc ID and it happened there too.
nikki added a comment - 01/Aug/12 02:01 PM It seems to happen when the medium has a disc ID. All the ones I've checked so far where it's happened have had disc IDs, so I tried editing a random release with a disc ID and it happened there too.
Kuno Woudt added a comment - 17/Aug/12 07:28 AM commit 995275da39fe2403494e0b93c62e5c61a3750984
(committed to mbs-4382 branch, will be shipped to beta once the other issues opened for that branch have been resolved)
Three more where it happens:


http://beta.musicbrainz.org/release/eb67a982-2dfa-4af5-8a76-0721dfd82dc6/edit
http://beta.musicbrainz.org/release/ed8ccdf9-ae44-4865-8fad-341c13d3ae16/edit
http://beta.musicbrainz.org/release/f219760e-a476-492e-b495-a9692fd02842/edit