Gragas super stun bug

I got stunned and was unable to move for about 5 seconds after a gragas slam or ult...I'm not sure which...The skarner in the game also said it happened to him earlier in the game...I was just stunned against the wall...and movement commands would not cause motion...After a few seconds...motion was restored...but it died from not being able to do damage while being damaged...FYI (there was not a poppy or vayne) and gargas was the only one with ability thrown where I was (It was not a jinx trap either....the duration was WAY too long)