You post a lot of weird problems, and I'm beginning to think that you do it on purpose. Anyway, maybe it's the discs you're using. Or possibly your laser.
Clean your laser lens and do a search for a pot calibration guide. Perform the pot calibration and your laser will become more powerful and hopefully get better at reading backups. Don't attempt a pot calibration tweak if you don't have a multimeter. You want a resistance reading no lower than 2.8 ohms. Between 3-6 ohms is normal.