It is not uncommon for more than one of a title to have the same mastering/manufacture defect.

It's possible there's a problem with the master.

A new DVD was always sent and was always OK

So this stuff happens.

have always received a perfect dvd back

May be you were just unlucky and there is a batch of bad DVDs out there.

The CD was actually broken. I returned it and requested a replacement; they sent the same broken one back to me. Otherwise, though, Netflix has been quick and reliable.

... and just plain old mastering errors on others that will upset a small number of DVD players.

It could be a programming bug in the player too that makes it fail on certain disks.

DVD players are computers. Some are more tolerant of exotic copy protection schemes or errors than others.

Today I stepped on a slug!
Ewwww!
What else fascinating shall we share?

Well, I think its nice to see posts like the OP, its definitely a slice of "Americana" culture when we have this kind of thing to worry about!

Slug slime is icky and hard to wash off.

it had a major skip in it, brand new out of the case, and wouldn't make it past a certain point.

I took it back and exchanged it for another copy of the same movie, same thing happened. Took that one back and picked a different movie.

We went back and forth on that.

I sent it back with a note - got the kid's DVD back with a note telling me I had returned my DVD in the netflix sleeve. Called them, they understood, said send it back. Got it back AGAIN with note saying I'd sent back the wrong movie. They got it right the third time.