Quiz from Quizmaker'13 gets stuck in iPad

Have published a course to HTML wit SCORM tracking and running it from Moodle.

When I view the course in my iPad, everything (apart from the logo background) looks fine until I get to a quiz question.

When I try to answer it, it allows me to select the right choice, but when I tap on "Submit", the button goes transparent and won't display the feedback, so I can't move forward to the next screen either (which would be useless anyway because I need to display feedback).

if I tap on the menu and go to the previous slide, it will show the "Prev" and "next" buttons. Tapping on the "Next" button will take me again to the quiz question but this time it will display the navigation options but not the submit button. However it will not allow me to select any other option or move forward tapping "Next".

If I tap on the next slide title in the menu, then it will resume. Going back into the quiz will render the same results.

This has happened in various quizzes, not just one, and they all behave consistently.

Is this something to do with iOS7 and Safari?

Thanks very much!