What is happening:
While in rooms with mobs, (esp. the mines with the lantern monsters) there is often attacks from clearly thin air with no mobs in the direct vicinity. (in addition, some attacks from regular mobs are VERY long-range compared to the actual animation)
I have heard others on the Discord chat have such a problem as well. I experienced this problem as a filly, but not as an adult unicorn.
Linux 64 bit, but the other people that experienced this has various other operating systems, so it should be universal.