The act 1 bounty “jar of souls” becomes incompletable. I have had this do two things
1: all monsters have been destroyed but the quest still says to destroy all the monsters.
2: after destroying the jar the quest still says to destroy the jar.
At times the jar becomes destroyable before the timer is up. If you destroy the jar at this point it is almost certain to become bugged with number 2. If you wait to destroy the jar till the monsters are destroyed then there seems to be a 50/50 chance of number 1 happening and number 2 can still happen but not at a 100% rate as destroying it before hand.