Just for the input, I get lots of trouble with maxwell too.
Well the problem is often the export plugin that send the geomtry into maxwell ... for some reason the vertex normal is lost, or discard.

It happends to me with modo to maxwell and 3dsmax to mawell ... for both package the MoI object was rendered fine using native render engine.

The only way to succesfully export moi geometry into maxwell with 3dsmax was to use npower nurbs for max ... but it's a really expensive solution (and I get many trimming
surface trouble when I test it).

That said it was 6 months ago ... maybe they fix it with recent release.