I hade it last year, then finally reinstalled new windshild ...and new sensor.
if new r/sensor installed , it must be reprogramed with on board computer..via pro-mechanick bmw facilityes --is preference ( same reprogramming if new windshild!) Or combination of this two.
in ur situation could be software feilier, related to rain sensor ( it meens u might not need to buy a new r-sensor - 199.00usd!or a new windsgield ) but reprogram software.
Short history of my story was:...- one bozo, who had this car before me( probably leased ) , decided to install cheaper version of windshild and also broke short plastic holders for rain sensor itself on the windshield inside car (which was not origin bmw windshield). So.. firstly it took of me a lot of time to varify what exactly is going on, after,.... how to deel with it ..ets..ets..ets..