Custom fields indexed incorrectly.

Hi folks,

I created several custom Processor Plugins and have issues with them.

For example. I have paragraphs attached to node which has textfield for manual input language. I created processor plugin which parse them into array:

  /**
   * {@inheritdoc}
   */
  public function addFieldValues(ItemInterface $item) {
    $entity = $item->getOriginalObject()->getValue();
    if ($entity instanceof Entity && $entity->hasField('field_price_table')) {
      foreach ($entity->field_price_table as $price_table) {
        /** @var \Drupal\paragraphs\Entity\Paragraph $paragraph */
        $paragraph = $price_table->entity;
        if (!$paragraph->field_language->isEmpty()) {
          $this->addLanguage($paragraph->field_language->value);
        }
      }
    }

    if (!empty($this->languages)) {
      $fields = $this->getFieldsHelper()
        ->filterForPropertyPath($item->getFields(), NULL, 'emasrussia_price_table_languages');
      foreach ($fields as $field) {
        $field->addValue($this->languages);
      }
    }
  }

  /**
   * Add language to an array.
   *
   * @param string $language
   */
  public function addLanguage($language) {
    if (!in_array($language, $this->languages)) {
      $this->languages[] = $language;
    }
  }

I added this field to the index:

The index is working great, but with mistakes. Index is running from Russian version of the site, and all indexed data for it is correct:

But then I switch to English site, here is an issue. The same views, same page, same index, same facets, but different result:

There must be only "English" available. There is no any node which contains Russian texts. This nodes even no translation to Russian ones, the are separate. Why did this happens? Maybe I have some mistake in my code. I check search_api DB table and it's contains 3 rows for each EN nodes with Russian labels. But where did it get them?

I have another bug, more interesting, but leave it before figure out how to fix current, maybe them are same.

I also use xdebug to see what happens, but no results, the array with languages is always correct.