Problems re-taking a quiz

I have a course with 5 questions at the end of the course.

The results page displays the result correctly and if the  learner does not get all the questions correct they have the option to go back to the start of the course, but when they come back through to take the quiz the second time you cannot click on any of the radio buttons to select an answer.

I have a " Reset Results" trigger on the restart the course button and set the five quiz slide properties to "Reset to initial state.

Has anyone else seen this behaviour?

Best Regards

John