Do you have a password manager installed, such as LastPass, Keeper, Dashlane, NordPass, or 1Password...etc
Do you have the Firefox/Chrome browser password manager enabled?
Do you have automatic form-fill in your browser?
Do you have any or a combination of the above enabled?
Do you have an add-on/extension enabled that manipulates browser cookies in any way?
Open your web browser in Incognito mode WITHOUT add-ons/extension (or load a different browser) then go through the process of updating your password from the user PREFERENCES page. Once you've updated your password to something new, you can return to change your password back to what you previously had. There is no password history check beyond validating your new password with your current password. UBB.threads does not keep a password history. And the current password is salted (one-way cryptography)