Each attempt builds on last with multi-page quizzes gives the wrong score on the second and later attempts

It seems that there is still something wrong with the "builds up on the last" feature when the questions are distributed on several quiz pages. The problem is that when a quiz with several pages is taken, the answers are recorded correctly for the first page.

Steps to reproduce:

1) Use Mdl 1.6.5+ code and create a quiz with e.g. 30 random questions on 6 pages (5 questions per page)

2) Take the exam and answer the questions on the 1st page: everything OK here, grade is OK and the answers are saved and shown correctly after the quiz. You might have e.g. 130 points at this moment.

3) Take the exam again and answer a question (or more) on the second or latter question pages.

4) Submit the quiz. Now your grade should be 160 point or more. What happens, however, is that your score goes down from 130 to 30, that is: your answers from the 1st question page are not calculated at all, even though you can see your answers for the 1st page (at the review quiz -situation). The answers are correct, but the resulting grade is not.

This bug must be closely linked to the bug I submitted some weeks earlier: http://tracker.moodle.org/browse/MDL-8958

At that time, the bug got fixed OK with one single question page, but apparently having questions distributed on several pages was a thing which none of us remembered to check.