The symptoms you describe sound a lot like you used a Planar Tracker on the face.
Yes you are right. I used fusion planar tracking, which stabilized one part of the image, in this case the subject's head. The way I tried it held the head steady and let everything else move.
As in this example (go to 4:48), which I followed in my attempt.
For stabilization, I set it to translation (x,y axis since there was only movement on the x), with and without camera lock. Again I'm pretty new to DR so I don't know why it didn't work. No change resulted. (I double checked with uncropped/zoomed original clip and the pan is not corrected by stabilization\translation).
When the camera inadvertently pans, the subject only moves about 6 inches to one side, which crops half of his left shoulder. Its very obvious in the clip since the crop window is tight around the subject.
Feeling that transform (zoom and position) and cropping (all sides plus softness) are interfering somehow.