Thresh hook off mouse?

My thresh has been awful this season despite him having been one of my strongest champions previously. While I initially decided that it was because of a new ISP or decreased skill, I began to notice that his hook goes far above the mouse cursor. The video shows what I see. The deviance is highest when the mouse is close to the horizontal axis, but I don't know what causes it or if there are any other factors that increase or decrease the effect. My friends tested this and had identical results on both windows and mac. Autocast was on for all tests.