Howdy Alex,
do you have your rear number plate in the camera picture ? I donīt know about the US plates, german number plates are strongly reflective (and they are white !!!) and the number plate lightning during night "flashes" out the camera by reflecting from the number plate. I mounted my plate as high as possible know and the software is doing better finding the right brighness setting.
Rear lightning is a joke as you mentioned, itīs only for showing "Iīm going reverse", lighning factor is zero. Unfortunatly, there are special bulbs in the X5, the standards from the petrol station do not work as they donīt fit in... Standard is a 16 Watt rear light, I will try and advance it to 21 Watt bulb, will keep you informed...
So long
Christian