Just discovered a serious bug: I went back and played a game without any of the Ascensions available, then abandoned it mid-game (using the “Abandon” option on the main menu) and played another (not sure if that’s required to trigger the bug), and then after that game ended in death, the character selection screen no longer offers Ascension 1 and 2 that I’d previously earned.
It may be relevant that I gained a level from that run.