2017 FORD C-MAX Visibilitywiper Problems

Rear back-up camera does not display on dashboard console screen when air temperature is cold, i.e. below about 45º, and will only turn back on when the car has sufficiently warmed up after driving some distance. This has been happening for at least two years. When the camera is not working, there is a blind spot directly behind the car. The rear of the car proximity warning signal still works, but the screen remains black. I brought this problem to the attention of the dealership service manager, who told me he could not find anything obviously wrong.