I think Max is OK. I believe that the problems were related to how you set up some things in the model. I'm sorry you spent so much time uninstalling and reinstalling. I'm returning the file to you in a private message. It has my changes. Some of them you may want to keep and some you may want to ignore but the main goal here was to determine if Max was malfunctioning.
You can reverse engineer my file to see what I did but I'll list the main things.
1. I disabled Exposure Control and the Environment Map in the Environment panel. I wanted to make sure they weren't interfering with my tests.
2. Material Override was Enabled in V-Ray Global settings but no map was in the slot. I turner that OFF.
3. I set GI to 'Brute Force'. It makes doing Progressive IPR renders better.
4. I imported my 2-sided material and used it for the tests since I knew it worked.
First, kudos for your naming of things. I do that even for files that only I see. It makes life so much nicer and faster. It's so difficult to work on people's files that have 1000's of 'box_001, box_002....' forever. Here are my suggestions and what made things work. Remember, there are multiple ways in Max to solve most things. This is just my way and it got it working. If you don't like my solution that's fine, you can create your own, but at least you know that at worst, "one method" works.
1. Your lanterns were objects with depth. You don't need the inside geometry. For the ones you see working, I removed all of the inside polys so that the lanterns are just one surface. That's why the 2-sided material didn't work. It won't work on a solid (manifold) object. It needs just a single surface. As soon as I deleted the inner polys they worked.
2. In the window opening of the building, there are backs on the pushed in openings. I'd remove those (as I did) so the windows punch through the wall like a real building. Then put the glass in to catch reflections. Put lights inside the room like a real space instead of having planar VRay lights in each opening that point out.
3. I UV mapped the spheres of the lanterns with a simple Spherical map. You had Planar maps or the default maps. It doesn't affect the transparency but does make them look better.
I likely changed a few other things, use them or don't, that's up to you. The main thing causing the problem was the inner faces on the lanterns and the solid back to the window openings. Fix those and you'll be good to go I think.
I'm attaching a few photos to show that things work but the Max file will come to you in a PM.
Rob Holmes
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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
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