As a warrior, if you got immobilized, then using hammer’s Earthshaker burst skill will cause your character’s animation appear as falling and you won’t be able to control your character – unless the immobilize condition is cleared in some way. The longer the immobilize condition is, the longer you lose control over your character, because while falling you can’t use skills. This happened in (Halloween) Mad King’s realm, fighting mobs.
It might have to do with how immobilize works with leap skills.