After some exchanges with Valentine thier suggestions agree with the above.
"If it's interference from the blind spot detection system, I would suggest activating the Traffic Monitor Filter (available only on newer units) or disabling the POP detection. For more information on programming, please click on the following link:
With more cars coming with this feature and interference source, maybe there will be software developed to set the sensitive of the rear receiver.
It isn't broken yet but I can fix that!
2013 550i Titanium Silver Metallic Dinan S3 , BMW F800ST, ML350