I would look at the trunk. Kelly just did a video about the trunk today. You can use a 10 day free trial if you are not a subscriber to search the newest videos. Look for all the videos about the trunk and go from there. Do a little bit every day and then make sure to focus on not letting yourself rotate to the left when you are sitting. As far as the shift in the squat, I would also look at things like reactive neuromuscular training (RNT) to work on correcting shifts.I’m sure you can find some explanations of how it works on you tube. Adding single leg work to your programming is also important.