When does a block tag is changed ?

The template is already part of the content, because my function outputs an h2 for the recipe name, even though I changed the recipe name block tag to be a span.

That’s why I’m confused and guess that the plugin is first outputting the base content, and then change the tags according to block properties.

I already tried changing the priority without success.

Yes I have. But actually, I think I tried to isolate the problem too much, and I’ve hidden the issue… my bad.

My ultimate goal is to display a table of content (that’s why I’ve first added anchors on headings). So for this, I’m using a shortcode that is calling a function.
I think the problem is that, at the beginning of my function, I get the content like so :

global $post;
$original_content = $post->post_content;

Is there anything I do wrong ?
It is obviously something wrong in my code, but my table of content works fine for content outside of the WPRM Recipe block.

Just in case, here is the page I need help with, and here is the complete code in functions.php:

function replace_ca($matches){
  return '<h'.$matches[1].$matches[2].' id="'.sanitize_title($matches[3]).'">'.$matches[3].'</h'.$matches[4].'>';
}
 
add_filter('the_content', 'add_anchor_to_title', 99);
function add_anchor_to_title($content){   
  if(is_singular('post')){
    global $post;
    $pattern = "/<h([2-4])(.*?)>(.*?)<\/h([2-4])>/i";
    
    $content = preg_replace_callback($pattern, 'replace_ca', $content);
    return $content;
  }else{
    return $content;
  }
}

function generate_toc(){
  global $post;
  $obj = '<div class="php-toc"><h2>Table des matières</h2><nav>';
  $original_content = $post->post_content;
  
  $patt = "/<h([2-4])(.*?)>(.*?)<\/h([2-4])>/i";
  preg_match_all($patt, $original_content, $results);

  $lvl1 = 0;
  $lvl2 = 0;
  $lvl3 = 0;

  foreach ($results[3] as $k=> $r) {
    switch($results[1][$k]){
      case 2:
        $lvl1++;
        $niveau = '<span class="title_lvl">'.$lvl1.'/ </span>';
        $lvl2 = 0;
        $lvl3 = 0;
        break;

      case 3:
        $lvl2++;
        $niveau = '<span class="title_lvl">'.base_convert(($lvl2+9),10,36).'. </span>';
		if ($lvl3 != 0)
			$obj .= '</ul>';
        $lvl3 = 0;
        break;

      case 4:
        $lvl3++;
		if ($lvl3 == 1)
			$obj .= '<ul>';
        $niveau = '';
        break;
    }

	if ($lvl3 != 0)  
		$obj .= '<li>';
	  
    $obj .= '<a href="#'.sanitize_title($r).'" class="title_lvl'.$results[1][$k].'">'.$niveau.$r.'</a></br>';
	
	if ($lvl3 != 0)  
		$obj .= '</li>';
  }

  $obj .= '</nav></div>';
  return $obj;
}

add_shortcode('table-of-content','generate_toc');

The change is applied if you want to check the page, but it fails loading.

I tried removing everything from the function except your code and returning an empty string, just to make sure that the issue is not coming from the regex or the loop, still not loading.