Embed controls 8 #table element?
It is no problem to put form elements in a table. See the example in core/lib/Drupal/Core/Render/Element/Table.php:

$form['contacts'] = array(
    '#type' =&gt; 'table',
    '#title' =&gt; 'Sample Table',
    '#header' =&gt; array('Name', 'Phone'),
  );

  for ($i=1; $i&lt;=4; $i++) {
    $form['contacts'][$i]['name'] = array(
      '#type' =&gt; 'textfield',
      '#title' =&gt; t('Name'),
      '#title_display' =&gt; 'invisible',
    );

    $form['contacts'][$i]['phone'] = array(
      '#type' =&gt; 'tel',
      '#title' =&gt; t('Phone'),
      '#title_display' =&gt; 'invisible',
    );
  }


Maybe you should start from here and then put step by step your code in this example and see when it breaks.