Is it actually 'pulling' its legs off or are they just falling off. I've had a red serpent for about 6 months now. Its doing fine now, but it did have some leg disentegration right after I put it in the tank. One leg completely broke apart and another lost about 2/3 of its length. They have partially grown back in the six months however.
My understanding is that they are very sensitive to pH changes and stresses which frequently results in their breakups.
If it is actively pulling the legs off though - thats bizarre!