Hopefully someone can offer a diagnosis/solution to my odd issue. When I turn off 2015 F-350 ignition, a small amount of current remains to dimly illuminate the LED taillights on the flatbed. The lights are so dim it’s not noticeable until dusk/dark. An auto electric guy suggested it may be “back charging” from the camper. It is causing the truck battery to draw down and occurs even if the camper power is shut down. Ideas??