[Gameplay] Stun/Root Issues

I've found recently that on occasion a stun or root will fail to root the enemy. Mostly in lux/veigars cases. IE: Veigar stun goes down.. Fizz can hop over it but then he used urchin strike (dash) and went through the stun; still applying the damage and not stunning him. The same has happened with Yasuo ult, Malphite ult, and a few others.

Note: None of them had QSS or Banshees