Problem with toon shading

A problem has been uncovered by the painting weights process and whilst I was playing around with the textures to give it toon shading. When the toon shading is on the rat, it does not move with the rig. It is like a separate object but this is deforming the rat whenever it tries to move.

James has tried painting the weights but it is like a joint is attached to the toon shading so when we try to move the rat, part of it will not move with it.

I cannot work out why this will not move but as soon as the toon shading is deleted, the whole rat moves perfectly. 

There are a few ways to resolve this:

1. Carry on with trying to work out where the connection between joints/weights and toon shader lies and solve it. 

2. Try to re-rig and re paint the weights to see if it is a glitch in the rig. 

3. Don't use the toon shader and try to find another method to create the 2D effect. 

The first two ways of resolving the issue could take quite a lot of time - me and James Tomkins have already tried for several hours to find where the issue is occurring but neither of us can find it. We even deleted the history of everything and James has already re painted the weights. 

To re-rig the rat could also take some time. It took me at least a few days to get the rig how it is now and it will mean having to put the other tasks on hold whilst this is done and sorted. 

The third option is the easiest at the moment as we are quite short on time and falling behind our schedule. We have discussed as a group other ways to give it a 2D look and we could try to use After Effects in post production. We do not have to have it with a 2D effect but it is preferable so the 2D effect may be something that we would have to think about dropping.