Decoy + Real Target: Using a Trickster, if you summon your Decoy and then cast Real Target on it, it bugs like crazy, blocks vision and even causes Critical Errors sometimes.
FoG "Tar Beetle": It casts a debuff called "Tar trap" which should only decrease 30% speed, instead it decreases your speed to 30% of its original value. Not to mention that it is present in all of the entrance rooms, instead of teleporting through the rooms casting the debuff like it has always been. It's bassically imposible to enter FoG without confroting this invencible mob.
Cancel: Don't really know if it's intended, but it only cancels random song/dances first and then random buffs once you have no s/d left, instead of globally cancel any of the buffs in whichever order.