Safari auto-generating incorrect password for a specific website on MacBook Air

When I try to log onto a single website Safari (17.6) enters the correct user name and password, but when I hit Login it replaces it with another auto generated password. I've removed the password in settings and keychain, restarted and reentered, but it continues to occur, but only for that one website.

[Re-Titled by Moderator]

Original Title: MacBook Air password issue