xinple

已找到原因:

/wpjam-basic/extends/wpjam-toc.php 文件中

将：

$object = wpjam_get_instance('toc', $post_id, fn()=> new WPJAM_Toc($content, $depth));

改为：

$object = wpjam_get_instance('toc', $post_id, function() use (&$content, $depth) {
  return new WPJAM_Toc($content, $depth);
});

原因是闭包导致 $content 未被修改。