Hi, there is a bug i thing if I set height of background for 100VH im still getting on my phone white strip. And there is no other choice but set static px but it would make white strip for devices with higher resolution.
So far there is one solution. Setting BG height : 1920px (FullHD) but then its useless for phones with lower resolution
EDIT: I hope I found final solution just set on background → position: fixed and background → overflow: scroll(auto). Its working for lumia 1020 , lumia 640(on landscape i got gray strips on each side , but its nothing in compare with white stripe at the bottom )