Rename
C:\Program Files\IronCAD\PDFViewer\Bin\IronCADShellExt.dll
To
C:\Program Files\IronCAD\PDFViewer\Bin\IronCADShellExt.dll_remove.
After that, see if it helps.
I think the facet display data was corrupt. I drug the whole thing into a catalog and back out to a new Scene. That recreates the facet data, all good.