[Burner]

When I try to maintain the bent right wrist in my follow through (both arms straight) I shank the ball. What am I doing wrong?

Strangling the grip with your right hand and overpowering your left hand's control of the club face in the process, is my guess.

Loosen that right hand grip a bit and give up control, in the right hand, so as to gain control in the left hand - where it belongs.