Hi,
I found, that there is a customization of the plugin results template files within the theme folder: https://i.imgur.com/43zbpWT.png
I recommend reverting the changes to the original file, or trying to make a change to that template file, to account for the empty titles, something like:
<?php echo !empty( get_field('woocommerce_intern_modelname',$r->id) ) ? get_field('woocommerce_intern_modelname',$r->id) : $r->title; ?>
Please consult with the developer who made the changes as well, to make sure it works correctly.