Why is wordpress not showing all search results (when querying MySQL they are), encoding?

Question

MySQL

Did a custom taxonomy search. I have this code:

<?php $search_term = explode( ' ', get_search_query( false ) );
    global $wpdb;

    $select = "
    SELECT DISTINCT t.*, tt.*
    FROM wp_terms AS t
    LEFT JOIN wp_term_taxonomy AS tt
    ON t.term_id = tt.term_id
    LEFT JOIN wp_termmeta AS tm
    ON t.term_id = tm.term_id
    WHERE tt.taxonomy IN ('customtaxonomyname')";
    $first = true;

    foreach ( $search_term as $s ){
      if ( $first ){
        $select .= " AND (t.name LIKE '%s')";
        $string_replace[] = '%'.$wpdb->esc_like( $s ).'%';
        $first = false;
      /*}else{
        $select .= " OR (t.name LIKE '%s') OR (tm.meta_value LIKE '%s')";
        $string_replace[] = '%'. $wpdb->esc_like( $s ).'%';*/
      }
    }
    $select .= " ORDER BY t.name ASC";
    $terms = $wpdb->get_results( $wpdb->prepare( $select, $string_replace ) );
    
    if ( count($terms) > 0 ){
      foreach ( $terms as $term ) {
        if ($term->taxonomy == 'customtaxonomyname') {
        //var_dump($search_term);
        echo '<article id="post-" class="attachment type-attachment status-inherit hentry">';
        echo '<header class="entry-header"><h2 class="entry-title"><a href="'.esc_url( get_term_link( $term ) ).'" title="'.esc_attr( $term->name ).'" rel="bookmark">' . esc_html( $term->name ) . '</a></h2><div class="entry-meta"></div></header>';
        echo '<div class="entry-summary"></div><footer class="entry-footer"></footer></article>';
        }
      }
      
    } ?>

If I set one word in the search (which is obviously in the names of taxonomies) - shows the results. I ask another (which is also there) - it does not show results.
At the same time, if I run the request directly in the database - the results that vorpress does not show, after the request to the database phpmyadmin shows.

Table encoding utf8mb4_unicode_520_ci.
In wordpress config:

/** Database Charset to use in creating database tables. */
define( 'DB_CHARSET', 'utf8mb4' );

/** The Database Collate type. Don't change this if in doubt. */
define( 'DB_COLLATE', 'utf8mb4_unicode_520_ci' ); - /* тут пробовал и пустое значение - все равно показывает не все результаты поиска*/

The encoding in html pages is simply utf-8. I know that from a certain version, the wordpress database encoding should be utf8mb4_unicode_520_ci. What does he not like, where to look?