R5 receiver problems
 

hi i was out bashing the other day and my Mad rat went crazy. It was only 100yards away and i had not put any throttle input in and it started to drive off on its own. There was no other RCers so i have ruled out interference so what could cause this as it is a 2.4Ghz. The straw had a rubber stopper on top of it if that helps and the transmitter had the aerial up.