Sejuani's E on Scuttle Crab

So basically there is this In-Game bug which SOMETIMES occurs with Sejuani when she tries to "permafrost (e)" the scuttle crab. Upon having 4 stacks on the scuttle and pressing e for the stun, you can see the permafrost projectile as it moves towards the scuttle crab but then disappears into the void . This is quite weird since the 4 stacks you had do not disappear but the skill uses mana and goes on cool down. However, you can use the E again once it's off the cool down. So basically the skill is "used on but not applied to the scuttle crab" to keep things short.