Probably needs to be calibrated again.
Requires mirrors and a set up, which BMW should be able to do, sounds like they being lazy and just want to sell a new unit.
Alberante has the setup to do the calibration
@Claudio - Alberante ARC did the calibration for my adaptive cruise when they replaced my radar unit and does so for most of the ARCs in JHB that don't have it.
If you replace bits of the driver aid system they will generally not be operational until calibrated. IIRC there are certain units (I am not sure whether the radar unit is one of them but the KAFAS cameras are one of these items for instance) that require an FSC/enabling code and coding. This can restrict you from using used parts in some cases (Probably at least in part for liability reasons when it comes to safety equipment) but there are ways and means of reinitialising these and buying FSC codes as well - looked into this when retrofitting things to my F10. If he did a repair using used parts, his issues may stem from this.
I can almost guarantee that the dealership doesn't want the hassle of trying to get this all to work and so says 'sorry can't be fixed'. There is literally nothing that is witchcraft or even rocket science on a car... especially one that came with the feature as standard
