https://www.youtube.com/watch?v=NtnjyoUNrjw&feature=youtu.be

I just finished clearing stage 5 and killing the boss (you can see I'm standing on the last slab of ice) when the troll that breaks the ice continued to spawn. It didn't allow me to clear the stage no matter how many times I killed it. I ended up just killing myself instead.

This is a huge problem for people who are trying to get on the leaderboard or even trying to clear it for the first time like myself.