The timing on when the Galaxy-integrated achievements come in seems to correspond only loosely to when I take the relevant achievement-worthy actions. For instance, I got the achievement for opening the Spider Door, not upon opening the Spider Door for the first time, but upon failing to open the Peacock Door a couple minutes later.

For a while, the pattern struck me as odd but not sufficiently so to be worth concerning myself with; but then I managed to get a sensation victory, which I very strongly suspect was supposed to come with an attached achievement, and nothing came. Which... in one sense isn't that big a deal, because I'm mostly playing for the gameplay, not for the achievements; but it still offends my achievement-related sensibilities enough that I figure it's worth bringing up here just in case it's not already a known issue.

(And also just in case it's an already-known issue and people have suggestions regarding how to avoid the problem.)

I can confirm having the same problem, though not quite to the same degree. Specifically, I got Peacock Door achievement not when I opened it, but only when I removed the card from the timer afterwards. Also, I never got achievement for dying from zero health and from being sacrificed. Most of the time, however, it works properly.