Quiz - loss of selected answer on last slide following review

I am creating a final quiz project. A test project has been set up in a blank project format using the default MCA slides. An intro slide  has been added with a button to start the quiz.

The student is to use the "Submit All" button on the slide of the last question to submit all their MC answers. The "back" and "next" buttons are available so the student can review and check their answers prior to using the "Submit All" button that is on the last question slide.

When published to HTML5, the quiz functions as expected except, when the "back" and "next" buttons are used to cycle through the questions prior using the  "Submit All" button, the selected answer on the last question slide (with the "Submit All" button) is cleared and has to be selected again. 

I have used Safari and Firefox to publish the test quiz,  both return the same error Your help and guidance please

Bob