@pdw Only thing I've been able to discern is it has something to do with "Fill passwords across affiliated websites."
F.E.
Opera will not offer to save passwords for:
"https://www.disneymovieinsiders.com/"
But it will fill in the login info using the credentials from an affiliated website:
"https://member.disneymovieclub.go.com/"
Why this is the case or how to get around this, I still have no clue.