That’s very strange, which V-Ray version is this? Is it possible to send us a stripped version of the scene with all the assets so we could investigate further? Also how often the issue occurs?
In order to check what’s going on we need to reproducer the issue in our environment.
Vray 3.50.04. The thing that complicates this is that it only happens on our renderfarm. We are using Deadline 8.0.9.1. I’ve never seen the proxy error on my desktop computer while rendering test images. Sometimes renderfarm slaves render the proxies correctly and sometimes they are black.