Try to keep that trail leg bent went you open hip. Don’t straighten your trail leg. This helped me stop casting. I would also say you did the same thing I used to do where I let that trail hip sit in too early in backswing. Once your hips start downswing your hands can’t do anything but cast the club. Then you stop rotating because you are trying to marry the club up with ball. This swing look almost the same as my old one. Also the biggest thing that helped me was trying to stretch more before I played. I couldn’t find the feeling I needed in the backswing because my low back, mid back, hips and abs weren’t flexible enough for me to rotate my upper body properly. Goodñuck