Really Annoying Xerath Q Bug!

Watch in .25x speed to see it clearly (I tried to edit the video to slow down but it seems youtube is still processing it)

It seems like Xerath Q is bugged. If you flick your mouse and then let go of Q, it will shoot where your mouse was before the flick. I have confirmed this happens to a friend too and was able to go into a custom game and do it over and over, so it is easily reproducible. I'm running smart cast + range indicators but that shouldn't really matter with Xerath's Q since its a charge up. This definitely did not use to happen as I flick quite often with Xerath (ya I know there's not really a good reason to flick all the time but it's a habit).