Sion Reverse Charge Bug?

I was walking in one direction as Sion and while my screen was scrolling in that same direction, I activated my ult to charge in the way my mouse was scrolling and the direction he was walking, but he suddenly charged in the direction behind him. He literally does a 180 and charges in the opposite direction he is walking. I am uncertain if it is due to camera scroll affecting where the mouse is located or something else.