I will inspect this weekend. BMW service record show the front brakes and rotors where done 30k ago and the rear brakes and rotors done 50k ago.
It is remotely possible an amateur mechanical friend of the owner replaced the rear pads, and I can believe he might have left the sensor wrong there but it doesn't explain the front brakes which I can't believe after just 30k would need changing in less than 5k. This why I posted about this something doesn't make sense with the cars stats. Well I will inspect and sort it out and report here. Sounds like a sensor may be worn ... but those I believe were replaced by bmw when bmw did the brakes.