Car/controller issue

Hi all
Ive just been messing around with my track and copper taped every joint to make sure I have a consistent power supply around the whole track. Anyway I had a few laps with both cars and both controllers trying every lane changer. One of the cars was very juddery and hesitant but now wont work at all. I cant seem to reset the car/controller, its just dead? Ive tried the chip in another dpr and still nothing so am I right to presume the controller is faulty? Any things I should try? Can I have both cars running from the other working controller to test the car?
Im still not 100% on how to assign the car to a controller so I might be doing something wrong.

I have done many searches trying to find a resolution.

Thanks
Christian