Does the CD drive sound like it's having trouble reading the games? Does the lens click or reset at times? If not then you have a hardware issue. Maybe a faulty CD system card or IFU docking station. I haven't come across a CD drive with these issues before but maybe some one else here has? Generally when I see those glitches it's system card or bad IFU. IFU might be repairable.
however, if you are having reading issues like slow loading times or clicking of the CD lens here and there as it's trying to read then maybe some minor potentiometer adjustments will take care of the problem