DVD Player Brightness fine increase doesn't work

When i increase the brightness in DVD Player 5.4, then there is no change visible while moving the slider until about one third to the right, where it immediately jumps to a too bright value. From there on the slider works as usual changing the brightness smoothly the more I move it to the right.

I usually brighten most DVDs a little, just a few percent, but this is not possible anymore with this behavior so that I have to use another player.

I trashed com.apple.DVDPlayer.plist but this doesn't help.

Any ideas?

PeeWee