I'm trying to add a release to this release group, by using an existing tracklist http://test.musicbrainz.org/release/add?release-group=b2b0f57f-2caf-31b4-a2b1-ad245c3c7af2

When I first go to the tracklist tab, I see an empty disc 1 with "Now loading tracklist..." (but there's nothing for it to load).

The "Use Tracklist" button at the bottom allows me to search for a tracklist to use, but when I click "Use this tracklist," it just adds another empty medium saying "Now loading tracklist..." indefinitely.

Since there was no disc 1 to begin with (it started out completely empty), I would expect it not to add another medium at first, but use that tracklist for the first medium.