Consider the following situation:

• Lesson with a cluster containing two questions. 
• Cluster is at the end of the lesson, set up to jump to next unseen question inside itself. Ending page is configured to jump to the end of the lesson.
• Student gives wrong answer to first question and chooses to continue.
• Student gives correct answer to second question. 
• While the feedback is shown, the student closes their browser.
• Some time later, the student logs in again and wants to resume the lesson.
• Moodle takes them to the starting page of the cluster. Cluster tries to jump to next unseen question, but there is none.

What I would expect to happen

The lesson jumps to the cluster's ending page and the student is taken to the end of the lesson. The lesson is registered as finished and the earned points are awarded.

What actually happens

Moodle sends its 'cannotfindpages' error page. The student cannot finish the lesson anymore, they have to start all over again.

I attached a demonstration course.