Sion Q and R stop working late game.
Played a longer rift game from team builder and Sion Q and R stopped working. I could hear the selection sound being made when pressing the correct key, but no ability was activated. This happened sometime after I achieved 800+ bonus health from sion passive. My total health was over 4500 around 40-50 minute mark. My only item I had with an active ability was the hydra. This specific match had a lot of stuns on both teams. I was stunned a couple times while charging my Q and a couple other stuns hit me during an R. I'm not sure if that caused the moves to bug out, but its worth mentioning.
Another player in the game spoke of the same instance happening to them in a different game.