Hi,
Thank you for getting back to me.
There was a further YOAST updated after the one that caused the problem and the latest update cleared the issue.
This is what usually happens ?? An update causes the 404 issues, quickly followed by a further update which solves them.
I will keep in mind your recommendations in case it happens again and report back.
Thank you for a great plugin it is very useful and easy to use.
Kind regards
Alex