i can't see much from the clip dude. i did notice your back is "humped over" (that's a highly sophisticated technical phrase). it's hard to place and hold muscle tension on your spine when you lean over that far. also, it looks like you releae the ball before the tension and energy in your body is released, but it's hard to tell.
post a video directly from the side showing your entire body and mound from your chest side. maybe we can see something.