One thing to really focus on while improving your game is keeping your shoulders in line with your knee. When you release the ball, your shoulders are way past your knees. If you make a video from the side of you bowling, and pause it at your release, and draw a line from your knee straight up, you dont want your shoulders to go any past that, but actually right on that line. It will also help your balance. Seems to me that you are kind of on your tippy toes at release, which is caused by your shoulders so far forward, and this is why you keep falling over to the side.
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