What card back are you using? I am not sure if this was already fixed, but there was a bug, that using Good Cheer card back make iOS devices unstable and prone to crashing. So just in case, make sure that none of your decks have that card back equipped. You might also want to disable Random card back if you have it, just in case it might be Randomly selecting you that card back.
EDIT: After looking in the last 2 Patch notes, I could not find any indication that this issue has been fixed. So again, make sure that your decks are not using Good Cheer card back.