Vertices not moving equally with equal weights.

I’m having some very odd behavior. I rigged the attached character, but only then realized that I was missing a jaw bone. I’ve put it in and created a vertex group for it. Here’s a picture of the jaw slightly opened. Obviously, some of the interior mouth is too strongly weighted, but I left it to demonstrate the more concerning problem. Although both the mesh and the weights are symetric, one side of the mouth seems to open fairly nicely, but the other is jagged and poorly behaved. Any guesses what is causing this?
Labratska108.blend (5.24 MB)

Checking the weights in edit mode, I can see that they are not symmetrical. You should be able to make this automatic by enabling X-Mirror in the tools shelf, then only paint one side of the mesh. Also, the weights are not normalized. This will become very confusing later if not fixed and if you do not know what normalized weights are.

I have a few weight painting tutorials on my youtube channel that deal with normalizing weights, auto weight clean up and a complete workflow for weight painting.

Good luck!

ps. Apply the transforms on the mesh and armatures. I would also recommend using a single armature instead of multiple unless you are making a multi character rig where wings for some characters will not be needed.

I obviously have a lot of work to do (And even more because of how I’ve done things), but the tutorials on your channel have pointed my in the right direction. Thanks!