Boroya: I came across a wraith, fought it with a perfect hit and dodge rhythm, only to realize that its health bar is empty but it isn't dead... anyone?
jwdR1: You might try turning the 'enemy level up-scaling' ON or OFF and see if that helps. I've been encountering several oddities with that feature. I haven't encountered your exact bug though. I usually run into level 1 bandit camps or monsters that take no damage even though their displayed levels are only 1-2 above my current level.
this one takes damage, all the way, health bar is empty, but can't kill it
