I have a 2015 V40 R Design, owned since 2016 and have a persistent problem with stones or pebbles getting caught between the backplate and the brake disc. This has happened maybe a dozen times in four years, doesn't affect the driving but of course makes a horrendous noise. It usually throws the stone after 100km or so as it wears down but is this a known problem. and is there a way to stop it?.