Thanks, that's very helpful! I have just assumed that I lost the tush line in/after transition, but now that you point it out, I see that I fall forward already in the backswing. This would also explain why I sometimes lose balance/fall forward in follow through, especially with driver.
I'll try the drills you mentioned - a couple of related questions:
1) Like you said, I push the hands away and take the club a bit outside on the backswing. I used to suck the club behind me/under plane and perhaps I have started overcompensating. Would you suggest trying to change this or just focus on the right hip turning deeper?
2) My right knee maintains a lot of flex (I think?) in the backswing. Would pushing the hip back be associated with straightening the right leg more in backswing, or should I maintain flex?