[Gameplay]Sion's Q and R locked?

After some playing i found that Sion's Q and R have stopped working. However his W and E will still work. those who play Sion know that his Q and R are his most important abilities

How i think this happens: a champion uses a stun/knock up on Sion while he hits his Q at the same time.

(example: Chogath used his knock up on me and i hit my Q when knocked into the air and it stopped working)

this glitch does not happen very often but when it does it can loose you the game the only way i have found to fix it is to re-log into the game. pleas fix.