Renekton Heimer grenade stun bug

Last game vs. renekton 3 or 4 times landed a grenade that should have procced stun. Turret lasers charged but no stun and no slow. It was at least .5 sec after his dash sometimes more.

It wasn't every stun, it appeared to still stun if he was just running but if I waited for the dash to finish and grenede while he was chaining his combo it resulted in no CC effect.