Ensure all questions on test are answered bug

Has anyone encountered the default popup message being generated telling the user that he needs to answer all questions to continue, even though all the questions have been answered? We have our test questions generally spread over 3 pages and we see this if the user clicks the Next Page button. All questions are single selection in a multiple choice format. We've been racking our brains trying to figure this one out. Test takers are in our retail stores and require a login so we can capture their Employee ID from the cookie. One associate can take the test with no problems while we get phone calls from another associate at the same store who can't take the test. We're not sure if it's Lectora or a systems/browser issue. Any ideas to troubleshoot this would be appreciated.

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