There's a major bug when drawing cards with the "on draw" effect, which causes the game to freeze and become unplayable. Seems to mainly happen when you draw 2 or more "on draw" effect cards.
Hello! I cannot recreate the conditions for it to freeze the game. However, I believe if the game lags in someway while playing, it MIGHT freeze the entire thing after the On Draw effects.
Lags may be caused by multi-tasking etc, or playing on old phones.