If a form contain a field define as password, the password will be replace by the login password when the form is loaded.
If the form is save the password will be overwritten by the login password.
Even if the password is suppose to be encrypt, the plain login password is saved without encryption.
If the View password characters option is on it will show the wrong password, the login password.
The only way to prevent that is to remove the password option on the field and it will work normally, except that the password will be visible in the form.
It need to be fixed as soon as possible