I think this kind of bugs are "normal", I mean, they are maybe occasional and wont repeat again.

I was playing against computer. I played the spell that makes opponent discard three random cards. Turns later, I played it again. When I was trying to target opponent for this second time, I wasn't able to do anything more for the rest of the battle. The time of my turn ran out but nothing happened. I don't remember, but maybe my opponent had less than 3 cards in hand, and this could have caused the bug.