Plugin not working properly and not detecting headers

There must be something special about those heading in your first article.

Please select the whole article, copy and paste it here like this:

<!-- wp:simpletoc/toc {"use_ol":true,"max_level":4,"className":"warning"} /-->

<!-- wp:heading {"level":4} -->
<h4>H4.sfdsdfsdf</h4>
<!-- /wp:heading -->

<!-- wp:heading {"level":3} -->
<h3>H3.sfdsdfsdf</h3>
<!-- /wp:heading -->

<!-- wp:heading {"className":"simpletoc-hidden"} -->
<h2 class="simpletoc-hidden">h2.hidden Ich bin neu und versteckt!</h2>
<!-- /wp:heading -->

<!-- wp:heading {"level":3} -->
<h3>H3.sfdsdfsdf</h3>
<!-- /wp:heading -->

<!-- wp:heading {"level":3} -->
<h3>H3.sfdsdfsdf</h3>
<!-- /wp:heading -->

<!-- wp:heading -->
<h2>H2.sfdsdfsdf</h2>
<!-- /wp:heading -->

<!-- wp:heading -->
<h2>Wahre Gr??e wen/oder nicht</h2>
<!-- /wp:heading -->

<!-- wp:heading -->
<h2>バウムクーヘン</h2>
<!-- /wp:heading -->

<!-- wp:heading -->
<h2>Olé Gar?on! Diese Sü?speise schmeckt gar nicht übel! *b?rp*</h2>
<!-- /wp:heading -->

<!-- wp:heading {"level":3,"className":"simpletoc-hidden"} -->
<h3 class="simpletoc-hidden">I have simpletoc-hidden as class</h3>
<!-- /wp:heading -->

<!-- wp:simpletoc/toc {"use_ol":true} /-->

<!-- wp:heading -->
<h2>?? ?? ????? ????</h2>
<!-- /wp:heading -->

<!-- wp:list -->
<ul><li>Testliste</li><li>Testlist</li></ul>
<!-- /wp:list -->

<!-- wp:heading -->
<h2>C<em>'est très chic</em> sasLa cédille</h2>
<!-- /wp:heading -->

<!-- wp:more -->
<!--more-->
<!-- /wp:more -->

<!-- wp:paragraph {"className":"warning"} -->
<p class="warning">Warning!!!! <a href="https://marc.tv">Link</a></p>
<!-- /wp:paragraph -->

<!-- wp:paragraph {"className":"notice"} -->
<p class="notice">Notice! <a href="https://marc.tv">Link</a></p>
<!-- /wp:paragraph -->

<!-- wp:heading {"level":3,"align":"full","className":"relevanteE"} -->
<h3 class="alignfull relevanteE" id="customid"><strong>Relevante </strong><em>Entscheidungen</em> mit Klasse 5</h3>
<!-- /wp:heading -->

<!-- wp:heading -->
<h2>Mein&nbsp;pers?nlicher&nbsp;Kinofilm encoding</h2>
<!-- /wp:heading -->

<!-- wp:heading -->
<h2><a href="https://marc.tv">10 Stunden voller relevanter & spannender Entscheidungen…</a></h2>
<!-- /wp:heading -->

<!-- wp:heading {"level":4} -->
<h4>Pro-Tipp für noch mehr Spa?!!!</h4>
<!-- /wp:heading -->

<!-- wp:heading {"level":3} -->
<h3>3 Ordnung</h3>
<!-- /wp:heading -->

<!-- wp:heading {"level":4} -->
<h4>4. Ordnung</h4>
<!-- /wp:heading -->

<!-- wp:heading -->
<h2>2. Ordnung</h2>
<!-- /wp:heading -->

<!-- wp:heading -->
<h2>Die beste Grafik auf der PlayStation 4 Pro </h2>
<!-- /wp:heading -->

And I tested it with many pages in different constellations. It worked without a problem on all pages and lists all headlines.

Please update to 4.4.5 and report back.

Seems to work now.

Will update you if other issues arise.

Thank you.