Help! Vray Next Rhino 6 displacment map not showing

Hello everyone, I hope I can get some insight into a problem that I have been experiencing with Vray Next in Rhino 6.
The short version is that rendering effects of displacement map is unstable, sometimes it will work with a simple box geometry than the same material applied to a more complex second geometry will not render the displacement map effect. And most of the time the effect won’t render even with a simple geometry. I have tried everything including exploding the objects grouping them. nothing seems to be under control.