Disappearing geometry

[3dcrgr]

First I have to mention I have two identical workstation here and the problem happened on both.
Currently the scene works fine, renders fast, great, DR is setup correctly etc etc so I can't even send it because it all good under good old Windows 8.1.

So I wanted to keep up with the world and installed (clean, not upgrade) Windows 10 on both machine all together with the same good 3Ds Max 2016 + SP3, V-Ray 3.30.05, RC+FP, W&T, Crossmap etc. Everything is up-to-date, legit, licenses are all stored in an accessible network location and each workstation has its own dongle.

I opened the same scene that worked fine and hit render.
At 3.5K res with embree on - everything renders great.
At 3.5K res with embree off - everything renders great.
At 8K res with embree on - render crashes at light cache on both machines.
At 8K res with embree off - prepass are all fine but rendering randomly ignores portions of the scene. Some buckets render a wall, and some don't.
At 8k res with embree off and rendering only with a single render node that stayed at Windows 8.1 - everything is fine.

I reloaded my system drive image back to Windows 8.1 on both workstations. Opened the scene and hit render.
At 3.5K res with embree on - everything renders great.
At 3.5K res with embree off - everything renders great.
At 8K res with embree on - everything renders great.
At 8K res with embree off - everything renders great.

What is happening? I can't even send you the scene because its not defective or something.
Am I the only one around here with strange behaviors?

[Svetlozar Draganov]

Interesting case indeed, besides the windows is there anything else that is updated, like plugin versions etc?
Does the issue happen only on a particular scene or you have the same issue among other scenes too?
Would it be possible to collapse all the plugins information from that scene to a regular geometry/textures and run the same tests in order to ensure that the issue is indeed caused by V-Ray not to other plugins?
Can you show is a example of a good and bad image in order to understand better the difference between?