This edit failed, ultimately because a recording merge got voted through before this edit passed, but the underlying issue was that I could not for whatever reason get the last track linked to the recording I wanted to point it at. It kept trying to put the MBID in place of the recording name.

So I reentered the edit, and the medium came out ok but I missed the part where it was still trying to change the recording name. (I'm pretty sure I didn't click any of the "update recording" boxes when I was editing the release, either.)

I suppose it could be related to a userscript I'm using, but so far this is the only recording that's been affected. All the others that I've done the same way (copy and paste the URL in the Recordings tab of the editor) have worked fine. Not sure what's special about it, other than it's the last track.