That is what mine was doing and I thought it was the worms or the spools but it was the ESC.Mine would act like it was bound up but it was not,the ESC was lit up and the motor sounded like it wanted to go but it would not go without f/r throttle or wide open.I think my ESC is the same one as yours but it is a China made copy not Traxxas.This drove me nuts and I thought the drive line was bad.Now with the ESC motor wires reversed the only problem I have is reverse which I try not to use.