In the "Creeper Woods" level, a map border is missing, it allows the players to cross it and they will fall out of the map, losing hp. I recorded a video of the issue, maybe this will help you finding a solution.

Sorry for the low quality, but the max size of the video is 10MB, so I had to downgrade the quality. The bug is near the end of the level, after saving the 5 villagers.