Bottom Portion of Head Skin is not Attached Properly

If you make and load any customizable skin and change the bottom portion of your head, that part will appear to float below the rest of your head creating an unattractive looking skin. Unlike the rest of your head, that portion is not properly attached. Attached are some examples, and the incorrect portion is circled in red. In this example I have made my bottom portion yellow and purple, and as you can see no matter what angle (and even a straight on point-of-view) it is not attached properly.