I made a simple pistol model, unwrapped it, baked maps (normal and ao) and exported it as .fbx to substance painter. In the material window of substance painter, the uv unwrap of the model looks like the first unwrap I did (which i changed because it wasn’t good)
I followed “modeling weapons for a first person shooter” lesson for unwrapping and baking normals, and “texturing weapons for blender and substance” lesson for ao baking and exporting.
I tried unwrapping the whole model again, unwrapping and exporting only a part of it, copying a part of it to a new file and then exporting. None worked.