Im not sure how to export and import with separate materials if you could walk me through that stage, that would be great. I tried to use backface culling but still didn't work. Also it seems to be working in window's in-built 3d viewer completely fine. I have found that only specific meshes that share the same material with another mesh (the roof and walls) are the ones that are produced wrongly after importing (the crates and barrels are imported just fine). It seems like the problem is on godot's side.