It definitely happens that one dvd player will be better at playing scratched or defective content than another - just like happens with CD players. And I'm certainly aware of the sony "rootkit" computer drm they put on a few audio discs some time ago... But that was on a cd data track and had nothing to do with an audio cd player pushing audio out.

I'm not asking if they would be willing to add new DRM to a DVD - obviously the answer to that question is yes. I'm just asking how you know that is what's going on, or if it's even possible to do. Can play in player A but not in player B so it must be new DRM is pretty thin.