"Watch others also and see how on a Reverse Turn the elbow gets behind the body and is know longer level with the front of the ribcage. In other words the body moved and the arm didn't go with it."

This is usually because the upper body rotated too much and too soon.

Reverse turn CBM is primarily in the hips at the start, with the upper body turning only later in the step. If you try to turn your upper body early, maintaining a frame would require bringin your partner across into a left offset. To keep the right offset you have to keep what is almost a left side lead in the top. Dancers showing the problem you see are keeping their hands in the right position with their partner's body, but mistakenly allowing their shoulders to rotate too early, to an orientation incompatible with their partner's location. Broken lines at the shoulder joints then make up the difference...

Anonymous,
Is the result same in fallaway reverse slip pivot ( lady part ) if the upper part turns too early, too much, too soon ? Usually, I kept my head weight more left , my left shoulder and spine in line with my standing foot to reponse to man's position. Maybe , I ignored excessive upper body turn happened. Thanks reminding .
Ylchen