vray adv, after disabling DOF in camera i get black render

For some reason when i am using DOF in camera and then i turn it off, in many cases i get black render. all passes just black.
Mostly it happens in animation, but here and there also on single frame.

Which V-Ray version is this? Can you attach simple example scene?

it is latest update. i dont have atm some simple scene only big one. if i manage to scratch it down i will upload something.