Officejet_6500_E709n ubuntu printing preferences double sided yields conflict

[jan]

I installed HP Linux Imaging and Printing System (ver. 3.15.4) for my Officejet_6500_E709n
on an old ubuntu (lucid 10.04) system.
Now, I cannot print double sided anymore.

Using the Ubuntu printer properties , submenu Printer options, yields a conflict (Yellow triangle with excalmation mark) in the printer options.

A4 paper and double sided (long edge) yields a conflict.
In documents, I cannot select double sided anymore.

Apparently, the current HPLIP driver has some logic to determine the circumstances for double-sided printing, but the logic is flawed.
This I cannoy use the duplex option that worked with ubuntu (lucid 10.04) out of the box.