You're trying to correct what it looks like in the open/closed throw, but then when you go back to the other throws it's the same thing. It's a fundamental feel difference, you'll know it once you have felt it and it will be repeatable.
I think you are balancing your sternum/chest over your left leg, and that's why you get that tilt back out of posture.
Do one leg drill setup on left leg. Stretch your arms out by your side and lift your right leg. Be 100% stacked spine on left leg. Rotate around with arms out and leg out in balance. Then imagine you are doing RH backswing with your right arm out and let the right leg pivot with you under the arm, however it is balanced. Left arm can be way out to the other side to counterweight. But you should feel how you can be upright on the left leg, and after you turn very closed you can start to leverage off the left instep toward where the target would be behind you.
If you do this and push toward the target behind you, your right leg will eventually have to swing forward to catch your weight in a closed way. It would kick a ball if a ball was there.