Interesting. I've never heard about this before. I don't tend to notice stuff like that either - if a note or two is slightly out of tune. And if I do, it doesn't bother me.
There's one high "ooooooooo" in the background vocals in Most Of Us Are Sad that goes out of tune and comes back. Probably Randy. It does bother me a bit. I can't check now, but I think it's at the end.