After I've held the left mouse button for attacking a big groub of mobs it seems to be that my charakter target a non exist enemy. This bug appears few times. But at the last? level which is Obsidian Pinnacle this bug appears WAY more often. That makes the game unplayable because this bug still continue until I kill another enemy or switch the zone of this level. Warping to the team mate doesn't help. I hope this bug will fixed soon. 

At the last boss fight we skipped that fight because the bug which I mentioned above. My teammate run a bit down and triggered the boss fight.