"Retry Quiz" asks questions twice

Hello Heroes!

I'm having an interesting problem with a 14-question quiz in which the last question is a drag and drop interaction. The problem is that if the user fails the quiz with that last question incorrectly answered and retries the quiz (incorrect answers only), it first guides them through the quiz correctly, but after clicking SUBMIT on the last question, it takes them through the other incorrect questions again before proceeding to the results slide. 

Here are some conditions to consider:

• No slide layers on quiz questions
• All questions except last question have PREV & NeXT buttons enables, the last slide has PREV and SUBMIT enabled.
• All questions are set to automatically decide on revisit

Any idea what could be causing this? Thanks in advance for the advice.