I'm pretty sure they're from CMC Magnetics. Depending on how old the stock is and if it's been exposed to light, it could be the reason you're having issues.
Check the disc info with Imgburn if you're on windows. If you're on linux, dvd+rw-mediainfo /dev/sr0 should tell you the same info.
Thanks for the recommendation, mate. I didn't know it was a thing, really appreciate it.