Dan, your problem is not covered by the fix. The fix applies to a bug in PDF->PostScript conversion, where the generated PostScript does not allow duplex on PostScript printers. In your case there is a direct conversion from PDF to PCL. Please try as alternative driver for your printer "Generic PCL-5e printer" with the "Foomatic/ljet4d" driver for example.
Dan, your problem is not covered by the fix. The fix applies to a bug in PDF->PostScript conversion, where the generated PostScript does not allow duplex on PostScript printers. In your case there is a direct conversion from PDF to PCL. Please try as alternative driver for your printer "Generic PCL-5e printer" with the "Foomatic/ljet4d" driver for example.