This issue has happened sporadically. The closest I have been able to replicate the problem is as follows. When parallel parking, I shift the vehicle in Reverse. The rear camera turns on. After backing up and having the rear sensors beeping, I shift to Drive and try to fix the front of the vehicle. The space is a tight squeeze. So the front sensors are now beeping. I shift to Reverse, the rear sensor beeps are slow but my rear camera never turns on. When I shift to Park and then Reverse, sometimes I am able to get the rear camera to turn on. Otherwise, I now to have parallel park the old fashion way using side mirrors only. Good luck with parking.