Since the last release I'm seeing a lot of "C stack overflow" in Blizzard_AchievementUI.lua:1891 on GetCriteria while I'm in combat. Since you just adjusted how that's hooked, I'm speculating that this might be related...

Probably can guess what caused it. Didn't notice any issues but I was just chasing a thought when I wrapped the rest of the achievement stuff in another function hook. Don't think it does anything or really is needed so I'll revert that bit.