Strange results

Outline of my problems:

  • Different results with Nero CD-DVD Speed
  • Many coasters with TTG01 on NEC ND-3500A
  • Discs work only ‘sometimes’

Alright, I had the NEC ND3500 but was not happy at all with the burn results, plus the drive sometimes makes strange clicking noises almost like broken hard drives do (so I assume the drive went bad). Anyways, got the Benq1620 now and still have some weired results with my TDK TTG01 DVD+Rs (printable).

First, here is a result with a Ritek R02 burned on the same computer…

Now, this is a “successful” burn at 4x, but I get three different results in Nero CD-DVD Speed:

Note, the last one was done after a reboot (but other scans were done before this one):

Now, while I do NOT find in surprising that the results vary a little, I do find it interesting the drop of PI Errors from 968k to 588k quite astonishing. Furthermore, I did not take the disc out of the drive between the first and second test! When trying to copy the disc it would go slow and FAIL towards the end (sector not found or something like that).
But after the reboot, it would copy it (towards the slowing down a few times).

Now, this is my main problem:
Look at this scan from the TTG01 that I burned DIRECTLY after the other one:

This was just the next disc on the stack!!!

What is going on?
Is it the drive? Or the did I buy a crappy stack of DVD+Rs?
How can the results be SO different?