I had some strange errors with these discs and my ND 3500A (2.1B)... when burning with ImgBurn I noticed that the device buffer emptied several times. While this is normally an indication that the drive is adjusting its speed, it meant trouble for the MCC03RG20.
The discs didn't verify after the burn (drive's choice: 8x), and looking at the underside of the disc, it's easy to spot with the naked eye: There's a blank ring near the beginning. So part of the data wasn't actually written to the DVD-R without a warning. Burning the exact same image to another MCC03RG20 resulted in the exact same blank ring at the same location.
Then I tried to burn with 16x and this was impossible. Around the same time when the device buffer emptied the first time during the 8x burn it also happened during the 16x burn. But then after that it would constantly jump from <10% to >96% and write speed was at ~1.1x. ImgBurn wasn't even able to cancel the burn I had to reset the PC. :a The drive wouldn't stop to spin even after killing ImgBurn.
I'll bring the 25 spindle back to the store on Monday anway... But what I don't get is that the errors are 100% identical on all discs.