I have a question about the 'proximity sensors' on the rear bumper of the Model 3. I've noticed when driving that vehicles that show on my main screen which are in-front and on either side of my car show up as solid picture representations, while the vehicle/s directly behind me flicker and flash instead of remaining as a solid image, even when stopped at a traffic signal. Is this flickering normal or should the vehicles behind me show as solid also? Could this be caused by a bad rear bumper sensor. I am considering making a service appointment but wanted some feedback first.