function biwp_contributor_name($post_id) {
    $corporate = get_field('biwp_corporate', $post_id ); //get Corporate checkbox value
    if ($corporate) { //if Corporate is checked, use biwp_cname (Corportate Name)
        $name = get_field('biwp_cname', $post_id );
    } else { //if Corporate is unchecked, use biwp_gnames (Given Names) and biwp_snames (Surnames)
        $gnames = get_field('biwp_gnames', $post_id );
        $snames = get_field('biwp_snames', $post_id );
        $name = $gnames .' '. $snames;
    }
    return $name;
}

add_filter('acf/update_value', 'biwp_fix_contributor_title', 10, 3);

function biwp_fix_contributor_title( $value, $post_id, $field ) {
    if (get_post_type($post_id) == 'contributor') {

        $name = biwp_contributor_name($post_id);
        $new_title = $name;
        $new_slug = sanitize_title( $new_title );

        // update post
        $biwp_contributor = array(
            'ID'          => $post_id,
            'post_title'  => $new_title,
            'post_name'   => $new_slug,
        );

        if ( ! wp_is_post_revision( $post_id ) ){
            // unhook this function so it doesn't loop infinitely
            remove_action('save_post', 'biwp_fix_contributor_title');
            // update the post, which calls save_post again
            wp_update_post( $biwp_contributor );
            // re-hook this function
            add_action('save_post', 'biwp_fix_contributor_title');
        }

    }

    return $value;
}

add_action('save_post', 'biwp_fix_contributor_title', 12);

function biwp_fix_contributor_title ($post_id) {
    if ( $post_id == null || empty($_POST) )
        return;

    if ( !isset( $_POST['post_type'] ) || $_POST['post_type']!='contributor' )
        return;

    if ( wp_is_post_revision( $post_id ) )
        $post_id = wp_is_post_revision( $post_id );

    global $post;
    if ( empty( $post ) )
        $post = get_post($post_id);

    if ($_POST['biwp_corporate']!='') {
        global $wpdb;
        $name = biwp_contributor_name($post_id);
        $where = array( 'ID' => $post_id );
        $wpdb->update( $wpdb->posts, array( 'post_title' => $name ), $where );
    }
}