I usually hesitate to give advice on this forum since there are those that are clearly more qualified than I, but I see something done often by myself. It looks to me like you're dropping your inside shoulder into the turn, causing your upper body to dump in, causing the ski to stop. This may be caused by something earlier in the process (too much speed coming into the ball, handle separation, etc), but when I do it, my best coach in the boat (my son) just tells me to exaggerate keeping my reaching arm up. I mean really up. Doing this helps keep my shoulders more level, smooths out my turn, and helps transition from the turn to the pull more smoothly.