Hi. Harz (harry plus godzilla... huge fan...) here.
My experience in the field of 3d is new. I just have a problem with the 3ds max up loader. Particularly windows and things that have holes in them. I've been trying to import houses with windows but get flickering and extra mesh where there isn't supposed to be. In lumion, the problem is not there when I import max files. Does Sketch fab hate windows or walls with holes? I see interior space models and they have figured out how to add windows. I've even looked up tutorials on youtube but only tell me how to import. I have the skills and know how to render and texture. Windows just come out as a solid and black. I've downloaded the up loader and even tried manual method of texture burning. I still have windows not wanting to be windows. Lumion and the crysis engine have no issues. I even do clean up vertex points in max.