Head keeps pulling off when I turn my head via webcam

I'm proud to say I have really understood the basic layering and I have done a video on Youtube with just facing front.

But now I'm trying to make a head turn but anytime I turn on my camera the head will just pull off from the body. I thought there was something I was doing wrong, I deleted the whole project started again and it's the same error. The neck and everything is tagged correctly so what is the problem?

https://drive.google.com/file/d/13F_SPPMjYN-OewbELEVjmuI9QChXjwsn/view?usp=sharing