custom post type not showed with bootstrap 4 modal and template part

Question

I've created a showcase template part that will get all my custom post_type for a showcase. The problem is that I've 18 entries added and the template part will only show 10 entries. I've used a bootstrap modal to obtain a gallery effect, and it is generated inside the foreach loop that display the gallery attachments inside the modal, this will cause that every entry has a modal. I don't think that the problem is this, but here is my code, can everyone suggest me a fix for this?

<div class="row">
  <div class="col-sm-12 col-md-12 col-lg-12 text-center" id="title-col">
    <h1 class="display-4 text-center text-uppercase"><?php _e('Showcase') ?></h1>
    <p class="lead text-center"><?php _e('lorem ipsum') ?></p>
  </div>
<?php
$args = array(
  'post_type' => 'showcase'
);
$showcase = new WP_Query( $args );
?>
<?php if( $showcase->have_posts() ): while( $showcase->have_posts() ): $showcase->the_post(); ?>
  <div class="col-sm-12 col-md-3 col-lg-3" id="showcase-col">
  <a class="open-modal" data-target="#showcaseModal-<?php echo get_the_ID();?>" data-toggle="modal">
    <div class="card">
      <img class="card-img-top" src="<?php the_post_thumbnail_url('full'); ?>" alt="<?php the_title(); ?>" id="">
      <div class="overlay">
        <p class="lead text-center ovl"><i class="fas fa-search-plus"></i></p>
        <h4 class="text-center"><?php the_title(); ?></h4>
        <?php the_content(); ?>
      </div>
    </div>
  </a>
  </div>

<!-- Modal -->
<div class="modal fade" id="showcaseModal-<?php echo get_the_ID(); ?>" tabindex="-1" role="dialog" aria-labelledby="ProductShowcaseModal" aria-hidden="true">
  <div class="modal-dialog" role="document">
    <div class="modal-content">
      <div class="modal-header">
        <h5 class="modal-title" id="exampleModalLabel"><?php the_title(); ?></h5>
        <button type="button" class="close" data-dismiss="modal" aria-label="Close">
          <span aria-hidden="true">&times;</span>
        </button>
      </div>
      <div class="modal-body">
        <img class="img-responsive w-100" src="<?php the_post_thumbnail_url('full'); ?>">
      </div>
    </div>
  </div>
</div>

<?php endwhile; ?>
<?php endif; wp_reset_postdata(); ?>
</div>