I ran into a bug today in Quest mode. I had two characters (Merisiel and Kyra) both on their minimum cards (6 each), and they were both in Shadow Tower, which forces a character to recharge all cards and redraw at the start of their turn. Kyra encountered a Hell Hound, which she didn't defeat, resulting in both characters having to discard one card from fire damage. Kyra died immediately after that as she couldn't draw any more cards. Then it went to Merisiel's turn, she recharged all 5 of her remaining cards in her hand, drew those 5 again, and the game stopped working. Animations continued, but all buttons failed to function on screen, even the cogs button.
After that, I exited the game (but didn't shut it down) to see how to report a bug (which is via these forums, obviously!). After about 10 minutes I went back into the game, it was still on the Shadow Tower screen on Merisiel's turn, and the interface worked fine. My device is a Huawei something or other, I doubt this is device specific though.
I won't be monitoring this post in order to reply to anything, you should have all the information you need in order to reproduce the issue though