Check out the issue at the link below. You see the flickering and you will see the issue with the hair.
https://www.youtube.com/watch?v=mADkjHjAquY&feature=youtu.be
I spent an hour adjusting the key in FCP and it never changes anything even when it looks like it is adding more hair or images.
Does the color of the background you are inserting matter? When i put a dark gray background it takes away that extreme shake and looks better.
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