Quiz Score Is Changing

I am using Captivate 5.5 and am running into two separate (but possibly related) issues.  I have a course with a 20 question quiz at the end (all multiple choice or true and false).  Users are required to get a 70% (14 questions correct) to pass.  I have the  quiz set up where they can navigate backward and forward through the quiz.  Once they submit their answer for a question, they cannot change their answer.  I also have the option to review the quiz turned on. 

The first issue I am encountering is when a user answers questions, and then navigates back to previous questions before submitting the final question, there is one question which shows it was not answered (even though it was).  The quiz is set up so they cannot advance without answering the question, so they did answer it, but when navigating back it shows no answer was submitted.  The quiz is also set up so they can only answer a question once, so when they come across this blank question, they cannot answer it again.  Any idea why Captivate would basically vacate one of the answer to one of the questions when navigating back?

The second issue I am encountering has to do with reviewing the quiz after they have submitted their quiz.  So, let's say someone gets 19 out of 20 questions correct, when they come to the results page they will see their percentage and a message that they passed.  They also have the option to review the quiz so they can see what they got correct, and what they did not.  If they click on the review quiz button and then navigate through the quiz back to the results page, the score changes showing them they missed one more than they actually did.  So in the example I gave it would say they got 18 out of 20 correct, when in reality they got 19 correct.  I have test this over and over again, and cannot figure out why Captivate is changing the score.

Any insight on any of these questions would be appreciated.