Mouth Issues: Its stays open when I look to the sides.

Hi, 

I'm having this issue with my character I don't know how to fix it.

When I stand still it's perfect, mouth synch works, it's good.

but when I move to any side this happens:

The face is not staying neutral, even if I don't make any sound at all.

I'm assuming it's something to do with this:

but unfortunately, I don't know enough to fix this issue.

Please help.

Thank you