Some things to try:
I have recently started experienceing the same issue.
Do you have any furher updates on this as I have taken the steps you recomend and I can reduce the shaking but not remove it.
Can you post a video showing the problem you are having?
As Jeff mentioned earlier, if you are using your webcam in a dark room you can get poor face tracking results. Also be sure that you aren't side-lit either (such as when you have a sunny window to one side of your face).