function allow_ee_duplicate_contacts_api( $result, $args ) {

    if ( did_action( 'AHEE__EE_Registration__set_status__after_update' ) ) {

        global $did_first_reg;

        if ( $did_first_reg == true ) {

            $result = false;

        }

        $did_first_reg = true;

    }

    return $result;

}

add_filter( 'wpf_api_get_contact_id_result', 'allow_ee_duplicate_contacts_api', 10, 2 );

function allow_ee_duplicate_contacts_user( $contact_id, $email ) {

    if ( did_action( 'AHEE__EE_Registration__set_status__after_update' ) ) {

        global $did_first_reg;

        if ( $did_first_reg == true ) {

            $contact_id = false;

        }

        $did_first_reg = true;

    }

    return $contact_id;
}

add_filter( 'wpf_contact_id', 'allow_ee_duplicate_contacts_user', 10, 2 );