Lightbox not showing image caption

Your PHP generates this html for gallery grid item:

<div class="sh-image-gallery-item">
  <div class="sh-gallery-item">
    <div class="post-meta-thumb">

      <img src="https://www.coleopterafarm.cz/wp-content/uploads/2019/12/PICT9418-660x660.jpg" alt="Carabus (Coptolabrus) smaragdinus brannicki">

      <a class="sh-overlay-style2" href="https://www.coleopterafarm.cz/wp-content/uploads/2019/12/PICT9418-1024x768.jpg" data-rel="lightcase:imgCollectionsh-image-gallery-simple-Bi7XU3vsdZ">
        <div class="sh-overlay-item">
           <div class="sh-overlay-item-open"></div>
        </div>
      </a>

    </div>
  </div>
</div>

The problem is JS script a part of bundled js file https://www.coleopterafarm.cz/wp-content/themes/jevelin/js/plugins.js expects title="your title for image" attribute for <a class="sh-overlay-style2">

So proper HTML would be

<div class="sh-image-gallery-item">
  <div class="sh-gallery-item">
    <div class="post-meta-thumb">

      <img src="https://www.coleopterafarm.cz/wp-content/uploads/2019/12/PICT9418-660x660.jpg" alt="Carabus (Coptolabrus) smaragdinus brannicki">

      <a class="sh-overlay-style2" title="Carabus (Coptolabrus) smaragdinus brannicki" href="https://www.coleopterafarm.cz/wp-content/uploads/2019/12/PICT9418-1024x768.jpg" data-rel="lightcase:imgCollectionsh-image-gallery-simple-Bi7XU3vsdZ">
        <div class="sh-overlay-item">
           <div class="sh-overlay-item-open"></div>
        </div>
      </a>

    </div>
  </div>
</div>

This way JS will use title from clicked item and display it as it should. Also it's more a question to support of Jevelin theme devs https://themeforest.net/item/jevelin-multipurpose-premium-responsive-wordpress-theme/14728833/support Probably they've fixed it in next theme's update. Or you'll have to alter PHP yourself.

Now I finded this in plugins.js

title:null

I tried to change that to title:'_wp_attachment_image_alt' but it just showed text "_wp_attachment_image_alt"