In order question type, when you preview quiz and you have more then one page, and you set the order in the order question type and then click on next (navigation bar) to move the next question or page and then click previous the last order doesn't save, i think the problem is in the order/questiontype.php inside function save_session_and_responses the $responses = &$state->options->responses; return nothing but yet im not sure.
Regards, Ofir Ashery.