How is the grade computed? The initial grade is M, and each answer will lower (or at best keep) it. For example, if the record is perfect but you hear a background noise when playing, according to the guidelines it can't be higher than VG.
You might get weird grades while messing with the answers. Make sure the combination of answers is plausible in real life to get an accurate grade, e.g. a badly warped record is most of the time (if not all) also audibly warped.