Mahjong Sanctuary: Hippos never use Mud Bath

You have a bug in Mahjong Sanctuary. I have 2 hippos - they both swim, but only one of them eats and sleeps. Neither of them ever use the "mud bath" area. I even upgraded that one task to see if it would make a difference, but nope. All the other animals cycle through eating, drinking, and sleeping except the Hippos. They spend the majority of time underwater instead of actually using any of the items we've bought them. Please fix this.