Yes. I was trying to identify if it was laser failure. If it was failing (in my observations of a normal slim), you would kind of notice a faint clicking sound of the laser trying to read the disc (rhythm of half seconds or so). Laser activity seems to be silent when at optimum. As GoSpeedRacer said, Gt6 is a dual layered disc which tends to put more strain on the laser. From what you described imo, is a sign of the laser weakening. But this is just my guess.