Quiz (Question Set) crashes in Blackboard Open LMS (formerly Moodlerooms)

1. Detailed steps to reproduce the bug (exactly how and when did it happen)

 After the user has retried the quiz several times, h5p content crashes and as a result all navigation buttons disappear.  The problem happens when the user repeats the following procedure 3-5 times in Blackboard Open LMS course.

1.  Open the H5P Quiz (Question Set) and give so many incorrect answers that you will not pass the quiz
2. Navigate back to courses front page or to the previous activity
3. Navigate back to the H5P Quiz (Question Set). Usually the user is directed to the last question of the quiz instead of the first question.
4. Retry the quiz and give so many incorrect answers that you will not pass the quiz
5. Navigate back to courses front page or to the previous activity

 The problems does not happen when the user logs in as a guest and his score is not saved to LMS. It does not happen either when using the same content with h5p-version 1.10 (2018082200) in Moodle 3.4.

After setting “Randomize questions” off, the buttons do not disappear, but the quiz starts from the last question.

2. Platform and version number. E.g. Drupal, Wordpress, Moodle.

 Moodle-based Blackboard Open LMS (formerly Moodlerooms)

 3. Mobile or Desktop

Desktop Windows 10

 4. Browser: Chrome, Firefox, Safari etc

 Chrome, IE 11 & Mozilla 60.3.esr

 5. H5P plugin version

 1.9 (2018053100)

 6. H5P content type and version (if a content type was used), and a sample URL or attached H5P.

 Quiz (Question Set) see the attachment

 7. Any browser console errors

 TypeError: mlink is null

 The error is propably not caused by h5p, because it occurs also when opening other acitivities and courses.

 8. Screenshots if it's a visual problemSee the attachment