Had yet another hardlock. Not 100% sure what caused it. But both players had 100% block chance then the "hit sound" played over itself like 20 times at once and the game froze. I Think it might have been beak's on block triggered damage causing an infinite loop since we both had that item and 100% block.
Edit: Had it happen the next time facing the same opponent when we both had 100% block with Beak as well. So it seems easy to reproduce.