Incomplete sheds are an indication of humidity that is too low. What is your current humidity? (It needs to be 50-60% all the time and around 70% during shed)
Here's a good thread for what do to about a stuck shed. You could also let the snake sit/slide through a lukewarm damp pillowcase or towel. I would recommend increasing humidity in the tank until the shed is gone.

What are your conditions like in the tank?