During the boss battle with the Wraith King, I got into a strange kind of glitched state, where my hero bounced around behind the Wraith King. My hero was still able to attack, but the Wraith King advanced all the way to the left side of the screen, and the units spawning right in front of him refused to attack. With my hero only attacking newly-spawned enemies behind the Wraith King, and the rest of my units not attacking, I definitely didn't have the damage to win, and had to retreat.