Variables not rendering on twig template

Try to insert new variables to render attributes on tags.
Got one working and two others not with almost the same data.
content_attributes variable is rendering OK, but sidebar_first_attributes and sidebar_second_attributes show no results.
This is a fork of Bartik Theme, with two basic overrides:

bootstrap_barrio.theme

<?php
/**
 * Implements hook_preprocess_HOOK() for page templates.
 */
function bootstrap_barrio_preprocess_page(&$variables) {
  $width = _bootstrap_barrio_content_width(!empty($variables['page']['sidebar_first']), !empty($variables['page']['sidebar_second']));
  $content_width = 'col-md-' . $width;
  $sidebar_first_width = 'col-md-' . theme_get_setting('bootstrap_barrio_sidebar_first_width');
  $sidebar_second_width = 'col-md-' . theme_get_setting('bootstrap_barrio_sidebar_second_width');

  $variables['content_attributes'] = array(
    'class' => array (
      'main-content', 
	  $content_width ),
	'id' => array ( 'content' ),
	'role' => array ( 'main' ),
  );
  $variables['sidebar_first_attributes'] = array(
    'class' => array (
      'sidebar', 
	  $sidebar_first_width 
	),
	'id' => array ( 'sidebar_first' ),
  );
  $variables['sidebar_second_attributes'] = array(
    'class' => array (
      'sidebar', 
	  $sidebar_second_width ),
	'id' => array ( 'sidebar_second' ),
  );

  if (theme_get_setting('bootstrap_barrio_content_offset')) {
	$variables['content_attributes']['class'][] =  'col-md-offset-' . theme_get_setting('bootstrap_barrio_content_offset');
  }
  if (theme_get_setting('bootstrap_barrio_sidebar_first_offset')) {
	$variables['primary_attributes']['class'][] =  'col-md-offset-' . theme_get_setting('bootstrap_barrio_sidebar_first_offset');
  }
  if (theme_get_setting('bootstrap_barrio_sidebar_second_offset')) {
	$variables['secondary_attributes']['class'][] =  'col-md-offset-' . theme_get_setting('bootstrap_barrio_sidebar_second_offset');
  }

  switch (theme_get_setting('bootstrap_barrio_sidebar_position')) {
	case 'left':
	  $variables['content_attributes']['class'][] = 'pull-right';
	  break;
	case 'both':
	  $variables['content_attributes']['class'][] = 'col-md-push-' . ( theme_get_setting('bootstrap_barrio_sidebar_first_width') + theme_get_setting('bootstrap_barrio_sidebar_first_offset') );
	  $variables['primary_attributes']['class'][] = 'col-md-pull-' . ( $width + theme_get_setting('bootstrap_barrio_content_offset') );
	  break;
	case 'right':
	  break;
  }
}
?>

page.html.twig

    <div id="main-wrapper" class="layout-main-wrapper container clearfix">
      <div id="main" class="row clearfix">
        {{ page.breadcrumb }}
        <main {{ content_attributes }} >
          <section class="section">
            <a id="main-content" tabindex="-1"></a>
            {{ page.content }}
          </section>
        </main>
        {% if page.sidebar_first %}
          <div {{ sidebar_first_attributes }} >
            <aside class="section" role="complementary">
              {{ page.sidebar_first }}
            </aside>
          </div>
        {% endif %}
        {% if page.sidebar_second %}
          <div {{ sidebar_second_attributes }}>
            <aside class="section" role="complementary">
              {{ page.sidebar_second }}
            </aside>
          </div>
        {% endif %}
      </div>
    </div>

This is the rendered output over a clean Drupal 8 installation:

<div id="main-wrapper" class="layout-main-wrapper container clearfix">

  <div id="main" class="row clearfix">
        <main class="main-content col-md-9 col-md-push-3" id="content" role="main">
          <section class="section">
            ...
          </section>
        </main>
        <div>
            <aside class="section" role="complementary">
               ...
            </aside>
          </div>
  </div>
</div>

content_attributes variable is rendering OK, but sidebar_first_attributes and sidebar_second_attributes show no results.
Override variable information, changed names, clear caches, uninstall and install theme, and finally install fresh Drupal. Same bug always.