Preactivate your right pectoral and lat( depress shoulder), move your shoulder socket towards C7. You've got to train that shrug out, it is a death move. You might overdue it for a while and it will cause problems. Eventually you'll turn it over to the computer and your alignments will be restored.
Root cause is likely setup and/or flexibility.
Bumpy
This is great stuff, guys. Bumpy, you're right. It is a death move that causes all kind of over the top action coming down. I've worked diligently on moving my shoulder down plane during the downswing as well. One question--is C7 my upper vertebrae? Should I focus on moving my shoulder socket towards my vertebrae as I turn back?