The only thing I can think about it, do you have death state occurring when HP equals zero, instead of less than or equal? Ah well, that's a minor issue and I had fun playing it, I might even revisit it to find more optional stuff, so good job :)
i fixed it earlier and put out fixed builds. the issue was that the preceding boss subscribed to the players defeat event, so when that preceding boss was destroyed the event invocation caused a nullreference exception and that caused the defeat method of the player to fall apart
