Is there a possibility to send us the good and the bad scenes for investigation?
Since the issue occurred just after the glass-material was added have you tried to remove that material and associated objects with it?
What render manager are you using? Have you tried to open the scene on one of the network machines and start the render locally?
Have you tried to reset V-Ray render settings?
Try to disable Global Option one by one starting from Displacement and Viewport Subdivisions if the issue still persist continue to disable the other options gradually.