PHP配置文件生成器错误

根据我们的新遗迹，在过去的30分钟里，出现了52个类似的错误。

Error: 
Non-static method PB_Label_Wordpress_Creation_Kit::wck_generate_slug() should not be called statically
Stack:
…at /var/www/sitename/wp-content/plugins/profile-builder-labels-edit/
index.php (96)
in pb_label_edit_create_box called at ? (?)
in call_user_func_array called at /var/www/sitename/wp-includes/plugin.php (503)
in do_action called at /var/www/sitename/wp-admin/admin-ajax.php (44).

index.php的一部分是：

function pb_label_edit_create_box(){
        global $wppb_strings;
        if( is_admin() && current_user_can( 'edit_theme_options' ) ){
                //var_dump( $wppb_strings );
                $pblabel_fields = array();
                $pblabel_backup = array();
                foreach( $wppb_strings as $filename => $strings ){
                        /* set up the fields array */
                        $i = 0;
                        foreach( $strings as $string ){
                                if ( !in_array( $string, $pblabel_backup ) ) {
                                        $pblabel_fields[] = array(
                                                'type' => 'textarea',
                                                'title' => $filename . '_' . $i,
                                                'description' => 'Default: ' . $string,
                                                'default' => $string,
                                        );
                                        $pblabel_backup[PB_Label_Wordpress_Creation_Kit::wck_generate_slug( $filename ) . '_' . $i] = $string;
                                        $i++;
                                }
                        }
                }

这种情况已经发生了一段时间，有人知道是什么原因以及如何解决吗？