Sion's Q and Ult disabled until exiting and reconnecting

I main Sion and on two separate computers in several matches I wind up being unable to use my Q or R even when nothing should be stopping them. There's no visual indications that either ability is disabled but upon pressing Q or R all that happens is a little clicking noise. The only solution I've found so far for this issue is to exit and reconnect; this is a huge problem as late-game reconnecting means a huge disadvantage for my team for the next 2 minutes and when it's close to a loss I have to either risk getting reported for leaving or try to rely on my two AP attacks when I need every tool I can to help us win (I usually build AD). It seems to usually happen when my Q is interrupted or when I die while using my Q. I have no idea why it affects my Ult but I've never had one or the other be disabled by it's own. I've not included a picture because there's literally no visual difference when the bug is in effect. Sorry if this has already been reported.