For the longest time I thought that the scratch-free copy of
Robot Wars Arenas of Destruction that I got from CEX Disc Read Error'd because the disk was faulty, even though it's the second copy I've gotten from there that's done it. It was only when I tried out other Blue Disc games that I knew worked before I stopped playing them that I realised my PS2 could no longer read Blue PS2 discs. Took it apart, cleaned the laser with a nonabrasive brush and now it reads them again.
I can finally play Robot Wars after all these years. I made some amazing robots in my youth. One is literally just a spinning robot with spikes, a flamethrower and its stronger variant the Torch Cutter and I named it Cat Wheel. Really lethal.