Check that you can see quiz summary either with the TOC or clicking the "Next" arrow in the last page. Check that each question has the right status. Check that you can use the button "Return to attempt" to go to the page you were before going to the summary. In a quiz with free navigation, check that you can use the icons in each question to go to that question. In a quiz with sequential navigation, check that summary questions don't have any icon to navigate to the question.