Regarding the missing Forest objects in some buckets - any idea how I might trouble shoot this? I posted on the vray forum. Is there anything else I can do?
If the problem is reproducible at each render, i suggest to simplify the object until you get some change:
1) First, hide non-essential objects and set lower render settings (basically to speed up render tests).
1) Replace the custom object by a simple element (as a teapot).
2) Use a basic material without textures.
Basically trial and error, simplifying the scene at each step, until you find what is causing the problem.