Assessment Not Working - Please Help

I have a complex assessment that intermittently does not work correctly. I am using SL 2.7. My assessment has 3 question banks from which questions are drawn randomly. On the Results slide I allow learners to go back and retake the text if they fail (they must pass the test to get credit for the course).

Sometimes when they retake the test the results appear bizarrely, something like 36.2 for a passing score. I've taken a look at the variables and I've noticed that sometimes the %Results.PassPoints% variable changes from 8 (for 80%) to 15.2. Whenever this happens, the results appear bizarrely. Any idea of what's going on? Is this a known bug?

I know that I can't adjust a system variable, but it would be nice if I could. (This is a real problem with your software.) I would just set the variable to 8 every time someone starts the assessment. Does anyone know of a way to do this with JavaScript?

I'm on a deadline and I need to make this work quickly. Any help is greatly appreciated.