[GAMEPLAY] Sejuani E sometimes doesn't freeze Scuttlecrab

Occasionally (I feel once every 6 games of Sejuani) when casting Permafrost against a Scuttlecrab with 4 stacks the Scuttlecrab will not be frozen and no damage will be dealt. However the mana cost of 20 and the 4 stacks of Frost are also used up and the skill goes on cooldown. Every time that this bug has occurred for me (4-5 times) the Scuttlecrab has been pushed to a nearby wall by the skill Winter's Wrath, as such I believe it is a cause of the bug.

1. Use Winter's Wrath on Scuttlecrab, pushing it into a wall.
2. Get to 4 Frost stacks and cast Permafrost.