You might want to try a different pipeline and observe the results. E.g., export it as obj (and/or other file types) from DS and then try to import it into Blender, or other CC software you have (or even import it back into DS). Then try to export it in the format you need. You could also just try to repair it in a proper CC app, e.g., build new geometry matching the problematic geometry, apply the proper materials, delete the old geometry, and export.