Bard Stuns Broken

I was playing my normal game of bard when i started noticing my stuns where not working. For example when the champ would be right next to a wall i would use my q and it would hit the champ then hit the wall, but no stun would go off. This happened to me 3 times in a match. And i know it hit the champ cause you would see the damage go off on the champ. Doesn't make sense to me.