I have a Brushed and a Brushless pair of Wilderness bikes for several years. I've had the usual problems of broken battery connectors and minor things like that until one day my wife began complaining her Brushed motor bike wouldn't fully stop. If I pulled the throttle or battery conectors apart it would stop until throttle was reapplied.
I figured it was a throttle out of calibration or somthing but swapping out with my throttle didn't help. I took the controller apart and found two capacitors side by side had the bottom leads broke off. They were just loose inside the controller so vibration over time stressed and broke the leads. I simply resoldered back onto the PC board and hot glued them secure and all has been well ever since.
I can't imagine how this wouldn't happen to everyone eventually. The capacitors should be hot glued at the factory so they don't vibrate. I figured I would share this to save people from buying new controllers where they could simply do a solder and hot glue fix instead. It would be wise to hot glue before the leads break to take a proactive approach.