Head tracking Freaks out

Hi I am trying to do a short head track where a guy gets shot in the head (lovely) his head jerks back and the track just looses the hold. The corner points on the surface go haywire. Was just wondering if you had anytips for me im desperate.

IM using Mocha for AE 4.02 with AE 2014 edition.

Here is where it starts

 

Then goes all wonky about here

 

Hi there!

I would try using the shear setting only instead of perspective, that might get you better results. Are you attaching data to a null or to a corner pin? You can get away with a lot more using a null. You can also try tracking a different part of his head, maybe use his neck to anchor the data.

Please let me know if you have any questions and I will be happy to help you.

Cheers,
Mary