V. What you need to do is learn how to control your pelvis motion in the frontal plane (side to side rocking). Side plank is a very good exercise for this. So is spinning on your bike at such a high speed that you start bouncing out of the saddle, then slow down your cadence until you regain control and try to focus on maintaining solid contact with the saddle with your sit bones. It might help to think about keeping both sides of your waist long, kind of like you do when you do triangle pose in yoga. I also like the first two exercises on this video for training your body to control your trunk posture while you're doing things with your legs. It's functional because that's what we ask our body to do while we cycle.

Maybe those will help with the hip rocking.