Hi Mr Robville -
Thank you for your assistance so far. After some work with your assets I boiled the issue down to the FBX exporting from Cinema4D trying to calculate the Phone Smoothing for a large scene seems to lose information in the exported file. The error message from the editor will always be present because the engine does not know how to read Phong Smoothing, but the FBX seems to be able to store a limited amount of data which stores the calculated smoothing.
Long story, short. I would recommend exporting your scene in small chunks, individual assets with the common pivot (so leave them in position) and place all the assets which you have been able to bring into the engine with smoothing into a Blueprint to recreate the whole room.
Ultimately the FBX export options for Cinema 4D would need the option to store the calculated normals generated by the Phong Smoothing, then they should import without error and as a whole into UE4.
Thank You Again for your assistance -
Eric Ketchum