Well, it doesn't happen EVERY time I get hurt, but usually it'll happen when I'm trying to do an air attack (smashing them on the head, or shooting them) and then I'll collide with the enemy. I'll get knocked back and then Piko will freeze. After that it won't let me move out of her knock-back state. I'll play the game again (Cuz it's fun anyways ;) ) and see if I can give you any more details!