[Gameplay] Spellcasts not activating properly

This one is extremely noticeable on Xerath, where upon casting a full combo (E-W-Q) the Q will initiate for half a second and then stop, forcing me to have to reclick q to actually activate it. The animations for the Q will even appear to start during this time but will quickly cancel (not going on cooldown) and pretend like it never happened.

I first noticed this on Orianna, when I thought I was going crazy that my abilities weren't activating properly. If not for the fact that it's happening on more than ori, and the Xerath one being extremely noticeable I'd have shrugged it off and just assumed I was bad.

I smartcast with Shift, and to the best of my memory these bugs are occurring mostly, if not exclusively, when I'm comboing a lot of abilities at once with Shift smartcast.