Hmmm, what would cause this?...

 From:  Michael Gibson
671.3 In reply to 671.1 
Hi Will, can you please post the .3dm file for that object? It will help if I can examine the geometry over here.

But from your LW Modeler screenshot, it looks like those pieces are not booleaned or actually attached to the central piece, and it also looks like the outside module is an open surface, not a closed solid.

If you get things cut up and joined together, then MoI will know that those pieces are all part of one continuous "skin" and will have the normals all consistent between different pieces.

If you've got objects that are just positioned next to each other but not joined together, then MoI does not know that they are supposed to be connected, and each one will get processed separately. Then combined with this is that the normal direction for an open surface may not always point in the direction that you expect, but for a closed solid it always should. Mirroring will typically reverse the normals for an open surface.

The cracky thing looks strange... not quite sure what is going on there...

- Michael