I have the same problem also in Open World and its only on foliage assets, not the static assets. Also wanted to support VR, so these black flickers appear as soon as I switched from Deferred renderer to the Forward renderer. Going back to Deferred gets rid of them. So I dunno, I guess maybe its an actual bug where foliage assets just don’t work with the forward renderer atm.
*edit I figured out the setting that fixes it. You have to disable “Vertex Fogging For Opaque” which is enabled by default and only applies to the Forward Renderer. It seems this option basically just breaks foliage rendering.