Proxies disappear on random frames for animations

[ramy02]

We're rendering out thousands of frames on our internal farm and finding that all proxies disappear from random frames. Paths are all UNC, and it is not consistent to a particular machine or frame. Proxies that are instanced by Forest Pack are not having this issue. No idea why we're having this.

We're using Vray 4.02.04.28322 and 3dsmax 2017.

Any clues?