I've noticed over the last ~6 months or so that I no longer get achievement pop-ups while playing games (or even after exiting a game), but they pop up en masse whenever I launch SteamVR. It's like they're being banked behind the scenes and all pop up at once.

I've checked my notification settings and nothing is set to disallow notifications, and of course I've restarted Steam and my computer numerous times and the bug still persists. I'm using the standard client, up to date.