[_ck_]

So to be clear, it’s happening after you successfully submit it, not the message on the same page you type in the password right?

The password error only happens for two reasons, either the primary password doesn’t match the confirmation or the password is less than 6 characters.

The $_POST data must be making it through because you’d get a different error.

I assume you tried various passwords and aren’t using multibyte (unicode) password or with slashes in them.