So, I was doing a bounty mission as you do, collecting batteries for Dragon Mountain by killing Zilla troopers. I was using the Yumi weapon, which has a small chance of turning an enemy into a rabbit on hit. The transformation happened to a marked quest enemy, which seems to have confused the game since it immediately crashed to desktop. I know that the game isn't actually being worked on any more, but I thought that having the information out there might be useful.