I’m playing on iOS, version 2.1.1, and the game becomes unresponsive every time I defeat Misery at Nether Realm level 50, once I get to the screen showing I have received the Twin Swords of Misery. This is true both on my iPad Air 2 and my iPhone 6 Plus. The controls disappear, and no matter where I tap on the screen, I can’t close that dialog box. Because of this, I can’t progress in the Nether Realms anymore.
I have the same issue but on level 300 (which makes it scroll of Misery).