Problem with WP_query, tags, intersect

Hello, I have two post types
1) dwqa-question – question from DWQA plugin
2) product – from Woocommerce
I would like to assign the question from DWQA forum to detail by tags.

I tried this in functions.php, but the $rquery = new WP_Query($rargs) doesn´t work correctly. Could you help me, please?

function woo_new_product_tab_content() {
// DWQA TAGS
$dwqa_slugs = array();
$dwqa_tags = get_terms('dwqa-question_tag');
if (!empty($dwqa_tags) ) {
  foreach((array) $dwqa_tags as $dwqa_tag) {
    $dwqa_slugs[] = $dwqa_tag->slug;
  }
}

// PRODUCT TAGS
$tag_slugs = array();
$product_tags = get_the_terms($post->ID, 'product_tag');
if (!empty($product_tags) ) {
  foreach((array) $product_tags as $tag) {
    $tag_slugs[] = $tag->slug;
  }
}

// INTERSECT
$result = array_intersect($dwqa_slugs, $tag_slugs);
$rargs = array(
    'post_type' => 'dwqa-question',
    'showposts' => 10,
    'slug' => $result
  );

// WP_QUERY
$rquery = new WP_Query($rargs);

  if ($rquery->have_posts()) {
       echo '<ul>';
    while ($rquery->have_posts()) {
      $rquery->the_post();
      echo '<li>' . get_the_title() . '</li>'; }
      echo '</ul>';
  } else {
    echo 'no posts found';
  }
  // Restore original Post Data
  wp_reset_postdata();
}
add_filter('woocommerce_product_tabs', 'woo_new_product_tab');