I finally figured out that my laptop is interferring with the test questions. Specifically, my mouse seems to jump around and randomly change answers sometimes. Even if I doublecheck my answers before submitting wonky things can happen.
I'll have to use one of my USB ports and a separate mouse. I will also figure out how to optimally adjust the settings on my laptop. It's a Samsung Q530, just in case anyone else runs into this. I HATE missing a perfect score. Grrrr.