Trundles Pillar of Ice permanently stuns Scuttle Crab

I recently played a game as Trundle jungle and when I went to kill the scuttle crab I used the Pillar of Ice first next to or on the Scuttle Crab it seemed to be in its stunned animation, but didnt have the little purple stun icon over it and remained in that position until it died. However the scuttle crab acted normally if I used an auto attack or any other skill on it first.