Inconsistent DVD accessibility

[Ralf Mardorf]

In the old days one way of copy protection for the C64 was done by
writing content to a position of the disk, that requires a head bump.
The first generation of disk drives for the C64 had no protection
against head bumps, but later drives had a light barrier, to prevent
head bumps. It could happen, that legal bought software couldn't be
loaded by some drives.

IOW it might be that even today some kinds of copy protection are
simply insane, offending standards. Today this at least is known for
some windows software, that misuses the MBR.

Perhaps some DVD _burners_ that are aimed for computers have a
firmware, that doesn't allow to use them in the same way, as a DVD
_player_ for the TV can be used.