Get Related Posts For Custom Post Type by Custom Taxonomy

single.php

<?php
// Show related posts.
// Fetch taxonomy terms for current product.
$productterms = get_the_terms( get_the_ID(), 'work_categories'  );
if( $productterms ) {
$producttermnames[] = 0;
foreach( $productterms as $productterm ) {
    $producttermnames[] = $productterm->name;
}
// Set up the query arguments.
$args = array (
    'post_type' => 'work',
    'tax_query' => array(
        array(
            'taxonomy' => 'work_categories',
            'field'    => 'slug',
            'terms'    => $producttermnames,
        ),
    ),
);
// Run the query.
$query = new WP_Query( $args );
if( $query->have_posts() ) {
?>

<div class="row-full">

    <div class="grid__container_three_columns multiple-items" style="    max-width: 1200px;margin: 0 auto;">

        <?php
            while ( $query->have_posts() ) :
            $query->the_post();
            // You can delete or change the folow line - the code line below is to fetch second feature image https://wordpress.org/plugins/multiple-post-thumbnails/ 
            $imageurl = MultiPostThumbnails::get_post_thumbnail_url( get_post_type(), "secondary-image", NULL, "secondary-featured-thumbnail" );
        ?>

        <div class="grid__item grid__items_sc">

            <div class="grid__item_image">
                <a href="<?php the_permalink(); ?>"><img width="100%" src="<?php echo esc_attr( $imageurl ); ?>"></a>
            </div>

            <div class="grid__item_descr">
                <a href="<?php the_permalink(); ?>"><p class="title-st"><?php the_title(); ?></p></a>
                <!-- <?php //if( false != get_the_term_list( $post->ID, 'work_categories' ) ) {
                         //echo '<li>'.(__('Ver más:')) . get_the_term_list($post->ID,'work_categories', ' ', ' ', '' ).'</li>'; }
                 ?> -->

                <?php
                    // @codingStandardsIgnoreStart
                    $first_term_name = get_the_terms( $post->ID, 'work_categories' )[0]->name;
                    //var_dump( $first_term_name );
                    echo esc_attr( $first_term_name ) ;
                    // @codingStandardsIgnoreEnd
                ?>

            </div>

        </div>

        <?php 
          endwhile; 
          wp_reset_postdata(); 
        ?>

    </div>

</div>

<?php }
}// End check if $productterms.
?>