Hi Bruno, thanks for sending the file. It looks like the display mesher in MoI is having some difficulty on some of the surfaces in your model, I'm not sure exactly why yet. But the display mesher takes some shortcuts in order to do things quickly. When you export, the export mesher is used instead and it does a more careful job emphasizing quality more instead of speed. That's why your export behaves differently.

Can you post a screenshot of a problem area in Modo? I'd recommend trying the setting "Output: Quads & Triangles" when you export out from MoI to see if that behaves better than "Output: N-gons". It could be that Modo is having problems with some n-gons.

- Michael