How to render a paragraph field in Twig in correct language?
The problem is that FieldItemInterface::view() has no language parameter. Furthermore paragraph fields are not translatable (only the subfields of the paragraph entity are translatable). So when rendering a paragraph field directly, without going through the host entity render stack, the language information is lost.

My solution was to force the translation in a preprocess function:

function MYTHEME_preprocess_field(array &amp;$variables, $hook) {

  // field_banner_slide is a paragraph field which needs
  // translation AND is rendered directly, e.g. by using Twig Tweak's
  // {{ drupal_field('field_banner_slide', 'node', node.id) }} in page.html.twig
  //
  // don't to this for "normal" rendering, e.g. when using
  // {{ content.field_banner_slide }} in node.html.twig

  if ($variables['field_name'] == 'field_banner_slide') {
    $lang = \Drupal::languageManager()-&gt;getCurrentLanguage()-&gt;getId();
    if(count($variables['items'])) {
      foreach($variables['items'] as $key =&gt; $item) {
        if ($item['content']['#paragraph']-&gt;hasTranslation($lang)) {
          $variables['items'][$key]['content']['#paragraph'] = $item['content']['#paragraph']-&gt;getTranslation($lang);
        }
      }
    }
  }
}


For a better technical explanation see issue #2753201 on d.o