Anivia's stun/q when shot through a creep wave disappears

When i play as Anivia i shoot her stun through creep waves for farm and to try to stun the enemy champion too. recently ive noticed that when i do this about 20% of the time the animation disappears. you can still reactivate the stun but you cant see where the ice ball is. i really like playing anivia but this bug makes it pretty difficult to do so effectively