Oww my neck! Mesh goes weird when moved

As you can see from above my mesh gets very distorted if I rotate the neck bone one way on the Z axsis.
Also if I rotate the bone below the neck, the part of the mesh below that bone distorts also.

Do you have any ideas why this is happening. I know my mesh where the neck and head joins is a little messy, but the neck is fine and the middle as well. I am attaching the .blend file.
I am trying to keep the neck the same shape as it is now, just so you know, in case anyone gets it to work :slight_smile:

Thanks, Glenn

Attachments

Frank Bones (neck modded).blend (975 KB)

Any thoughts? I would like to move forward on his progress but am not sure what to do with this problem I have.

Glenn