Here's something I've been seeing in this latest version. Typically happens when an object is generated from imported geometry. Started as a closed spline that came in from a DWG. Extruded it up. Shows as a solid but looks hollow. Doc doesn't fix it. Tried reversing and converting it with no luck. Usually I can pull a face off and extrude it to make a new piece of geometry but no luck.
I did export it as a 3DS and re-imported it into Z. That one looks fine. There's something here the doc isn't seeing. Any ideas?