With Vectorworks 2018 (and maybe 2017 - I can't remember) I've been plagued by invisible 3D geometry - especially, and most consistently, by the invisible 3D geometry of hybrid objects contained within hybrid symbols when the 2D component of the host (container) symbol is edited.  The geometry is there (in 3D views), as expected: if I hover over it with the cursor, its preselection highlighting shows; and if I select it, its selection highlighting shows, and it's present in the OIP.  Otherwise,