Hi Michael,
Can you look at the viacad import of this model? Exprort part as sat for a solid, then export part as dxf.

Import both files. The dxf requires choosing "mm" as units to match. Is Viacad not reading something? Or, is your dxf not writing out the units yet?

Could it be related to dxf being somewhat "unitless" and just various things will not translate the same?

Thanks.