Just before my 3 yr warranty expired, I had one leaking valve stem. Ford said, normal wear and tear.Then, over the next three months, the other three all leaked.
I replaced them all with non ford parts at a local tyre centre, £30 each for fitting and balancing.
Apparently, the Ford valve stems are prone to corrosion, which creates small capillary leaks.
The fitter suspected that they were several years old and that Ford had been using up a huge backlog of old stock.
I was wrong once but then I could be mistaken.
2014 Bmax 1.6 Powershift Titanium X