I just installed 5 in an 87" EF Yak and they work flawlessly. And as much as people poo poo Hitec servos I have never really had a problem with them. I have heard however that if they are going to fail they will do it immediately. I too am running a LiIon 4800ma pack through a MPI miracle switch which also includes a 6v regulator. I would contact Hitec directly and send it back for replacement. Interesting note, of all servos I have ever heard having problems it's the 5945s.

Good luck

JP