Skipping slides

I have created some Captivate quizzes using Captivate 3 and outputting them as Scorm packages 1.2. They run in an LMS and all work fine on my computer. However, when other users tested the quizzes they had occasional problems where the quiz would skip a question. The only solution for them was to restart the quiz which is not very satisfactory. I tested the quiz in Firefox where it has always worked ok and my colleagues where using Explorer, Im not sure whether that is likely to be the issue. Has anyone else experienced this problem? Im wondering whether adding extra time to each slide would help or if there is a setting change I could make. Its difficult because it appears to be on random question slides.