Any time you get read errors from the drive, the first thought should be the Disc is bad. Usually that means the disc is dirty. Sometimes it means the disc is a bad pressing. Sometimes, the drive will not read a bad Disc at all. In a first-time-ever, I had a new permutation. The Laser for DVD and BluRay are different. I have had drives that had one or the other go bad. But recently I had a few BluRay Discs that would not read on the drive while others would. Since the 'bad' Discs read on a different (older and slower) drive, I was puzzled. Since the drive that would not read is a slimline drive, the read heads are there to see and I noticed that from one side the head looked dim and from the other the head looked shiny. I wiped the heads carefully with a microfiber cleaning cloth and low-and-behold.. two of the 'problem' BluRay Discs now work. I thought I would share this to help others. I was pretty surprised that it would read other BluRay Discs fine -- not even having reported bad sectors.