So, when doing various repetitive "quests" (i.e., wipe out all of one kind of nasty being in a particular place/area), I'm told they're all wiped out (well, the quest is "complete" anyway) when there are still some remaining.

Quite the bug, really!

edit: Not to mention, extremely immersion-breaking (e.g., "It's safe now for the -----!". No, not the only such thing, but it's a bad one!