M'nthster Glitch?

The same happened to me last night. I logged in, clicked through Bart's dialogue, and tapped the kids who had finished fighting. It showed I had defeated M'nthster (all tentacles were grey), but he wouldn't leave the campfire. I tried going to the friend screen and to Krustyland, but no difference. I selected the Fight option again for Bart and Milhouse, and let them fight for a bit, then stored the buildings to free the kids, and M'nthster finally went to the tower. However, after that I logged into my second town where the same glitch hit, and I couldn't get rid of him even though I went through the same steps. So, I left the kids fighting overnight and this morning the timer reset so they have to fight again. But, I cleared the task by tapping the empty tower. Whee