I Have just bought a 2015 bmax, not knowing of this fault, driving home from the dealer to the tyre pressure light pinging. Put some air in fine for a couple days then starts again, noticed the corrosion around the valves but never seen it before and wasn't aware it would cause problems. Soapy water all around, front passenger side valve stem leaking air. So replaced. Done 20k, kinda disheartened now knowing its going to be a constant hassle to add to cost.