The used movie dvd looked IMO clean, no scratches, very clean, even viewed
at a angle, could see nothing.

I played it and got, I believe, an unusual problem.

A scene in a lighted room, the lighting is bright as you would expect, but
a moment later, the lighting dims, then brightens again. This repeated at
random intervals during the viewing. The movie was "The Man in the Grey
Flannel Suit", and that was not in the movie.

I replaced it with another movie dvd, it played fine.

I washed the problem dvd in plain water, let it air dry. Now it has water
spots. Haven't tried to play it again.

What is a safe way to clean a movie dvd at home?

And, is a dirty dvd the problem in the above results?

ms