Looks like he used Ngons for the flat surfaces and the normals and triangulation got messed up. Are the holes in the sides supposed to look like that? This just seems like a problem with the triangulation and normals after exporting. If you can upload the OBJ, I could have a look at the topology in Blender and see if I can fix it for you. Otherwise, he may need to remodel this and avoid using Ngons and make sure the normals are all facing the right way before exporting.

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