Need help to manage several question banks

Hi everyone, I need your help...

I have a module containing 8 parts (videos) to visit. After each part, I have 2-3 questions included in a question bank. Questions are shuffled within each question bank. So I have 8 question banks. All the parts are reachable through a menu page.

What I would like to do: 

 At the first visit, the learner go through: menu > part1 > question bank 1 > menu > part 2 > question bank 2 > menu > ... > part 8 > question bank 8 > result slide.

If the learner is successful, this is the end.
If the learner is unsuccessful, he/she has the possibility to try again.

In this case, the learner comes back to the menu page and has several possibilities:
- review the videos: menu > part X > menu > part X > menu > ... (after each part, the learner comes back to the menu page, without going through the question banks)
- retry the quiz (new button): menu > question bank 1 > question bank 2 > ...  > question bank 8 > result slide (the learner goes through the 8 question banks, without going through the menu page)

The new button 'retry quiz' on the menu page is on a layer that appears when the variable Module_visited=True. This variable turns to True when the result slides starts.

What I have:

I have only one question of each question bank...

When I want to review the quiz (after being unsuccessful), the preview crashes...

I have attached my file. If you have any idea...