Mat I am using Moi in Modo and these kind of issues used to happen to me before I started using LWO as the export format in Moi. Since them Modo imports them perfectly. I suspect this is more a Modo issue than a Moi one as I occasionally see this flipping in Modo modeled meshes for some reason. Mesh clean up doesn't help either.

So if you haven't tried it use the LWO export option.