Over the years I've had a few of these oddities come up. You didn't mention what versions of Max and VRay you are using (which is always suggested) but it's likely not a bug but a misconfiguration. I've almost always solved them by doing and ENU reset and reinstalling VRay. Reinstalling VRay is pretty fast and easy.
For the ENU reset, do some reading beforehand. You can save a lot of time reconfiguring your custom workspace setup if you do it properly. But, it's a skill that you should get familiar with because ENU resets will save your life frequently. I have a backup routine that saves my current ENU every night. That way if one causes problems, I can revert to a known good one and keep rolling. I also have a pretty good post on doing an ENU reset and a list of the steps I take. If you search for that you can find it.
Rob Holmes
------------------------------------------------------------------------------------------------------------------------------------------
3ds Max (2023-2025), V-Ray 6.2, Ryzen 9 3950-X Processor, DDR 4 128MB, Gigabyte Aorus X570 Master motherboard, Sabrent Rocket NVMe 4.0 M.2 drives, NVidia RTX 4090, Space Pilot Pro, Windows 11 Pro x64, Tri-Monitor, Cintiq 13HD, Windows 11 x64
------------------------------------------------------------------------------------------------------------------------------------------