Daz I think you have hit the nail on the head...
my rustler has a low voltage detector, basically it slows the Rustler right down, here I think I should have been stopping and removing the battery, however, like a complete spoon, iv been running the battery until the Rustler totally stops.
only thing is, I have two of the exact same batteries which iv been doing the exact same with, yet only one seems to be playing up...