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Why do you think that it cannot be the media? Ritek discs are not exactly the very best, and the culprit could be the disc indeed.
Being the drive rather old, it could be at the end of its life, so it is a good idea to get a more recent drive, because most of media available in the market now are high speed certified, and there are very few probabilities that you'll get a firmware update for that drive.
The best solution seems a new drive :flower: