Blind spot monitoring

My mk111 1.4 SE L exec estate has a kink that is annoying me.  The driver's side blind spot monitor (bsm) is perfect but the near side only alerts when I overtake white vehicles with very low skirts ie white camper vans and even that can't be relied on.  It has caused me some concern in the past but this weekend we drove from Cornwall to West Sussex (dual carriage way for 200 miles) and I got SWMBO to monitor the monitor very closely whilst I overtook a variety of vehicles in a variety of manners ie closely (not too close), well clear, LH indicator on and off etc. the only times it alerted was when I passed white camper vans.  I bet Gizmo is going to tell me that the left hand floggle toggle has fallen off.