Hi Brian, thanks for testing this. The problem is that in both 4Box01.3dm and 4Box02.3dm the objects are not clean solids because more than 2 surfaces are coincident at these edges:



Having that type of geometry as one single object will cause various kinds of inconsistent behavior not just for .obj conversion but also for various other operations as well.

That should be separated out into 4 separate independent objects instead of being just one single object, that should then give a lot more consistent results.

I can understand that it is objectionable that MoI reports the object type here as "solid" but unfortunately it isn't really feasible for MoI to do an extensive self intersection test as part of the properties panel display. That's because such a test can end up being very time consuming especially on larger models and it would not be very good for everything to pause for say 10 seconds or so with every selection.

- Michael