We are having a company set up a virtual environment for our customers, so they can set up and see our products in a real world environment.  After I've saved the assembly as a part and selecting the exterior faces only option I then save it as an .stl file.  The issue is when saving the assembly as a part some of the geometry is lost in translation.  You can see the missing edges and faces in the screen shots.

I've tried the defeature tool, suppressing unnecessary features and components, inserting that part into an assembly and saving that as a part, but the new file is still missing the geometry.  The file size is too big when I save it with the 3d geometry intact.  So I'm not sure if I have any other option than 1 - manually fixing all the missing geometry.  or 2 - leaving the models as is (which my boss does not like).  Please tell me there is some easier way.