this is a problem with OSM and objects with multiple levels aren't handled very well.  I put the flyover into its own building and this is probably the best we can do to not have validator errors and hopefully this will also render properly in f4map/osmbuildings.  This is a very minor issue and not worth the effort to fix unless you, who doesn't like it, really wants to fix it...so go ahead!  Else this is probably the best it will go for now.  Closed.