How to import cyrillic users to wordpress site?

Question

csv

Hello! On a site running wordpress ,
the Cyrillic usernames plugin is installed .
Using the ClassiPress Ads Importer plugin , I import users with ads.
If the usernames are in Latin, then everything works fine, but if the authors are written in Cyrillic, then regardless of whether these are new users or existing ones, in the line

wp_set_object_terms( $post_id, array(intval($term['term_taxonomy_id'])), 'ad_cat');

I get an error:

Fatal error: Cannot use object of type WP_Error as array

, and the user himself has time to register (displayed in the admin panel)
I understand that the import works before the allow-cyrillic-usernames plugin has time to work out - how can I fix this?
classi-importer.class.php plugin file

foreach($rows as $row) {
  $post['post_title'] = $row['post_title'];
  $post['post_content'] = $row['post_content'];
  $post['post_status'] = $row['post_status'];
  $post['post_type'] = 'ad_listing';
  if(isset($row['user_name'])) {	
    $user_id = username_exists($row['user_name']);
          if(!$user_id) {
      $random_password = wp_generate_password(12, false);
      $user_id = wp_create_user($row['user_name'], $random_password);
    }
  }	
  unset($row['user_name']);
  $post['post_author'] = $user_id;
  if(!($term = term_exists($row['ad_cat'], 'ad_cat')))
  $term = wp_insert_term($row['ad_cat'], 'ad_cat');
  $post_id = wp_insert_post($post);
  wp_set_object_terms( $post_id, array(intval($term['term_taxonomy_id'])), 'ad_cat');

allow-cyrillic-usernames file

function acu_sanitize_user($username, $raw_username, $strict) {
  $username = wp_strip_all_tags( $raw_username );
  $username = remove_accents( $username );
  // Kill octets
  $username = preg_replace( '|%([a-fA-F0-9][a-fA-F0-9])|', '', $username );
  $username = preg_replace( '/&.+?;/', '', $username ); // Kill entities

  // If strict, reduce to ASCII and Cyrillic characters for max portability.
  if ( $strict )
    $username = preg_replace( '|[^a-zа-я0-9 _.\[email protected]]|iu', '', $username );

  $username = trim( $username );
  // Consolidate contiguous whitespace
  $username = preg_replace( '|\s+|', ' ', $username );

  return $username;
}
add_filter('sanitize_user', 'acu_sanitize_user', 10, 3);