Hello Roman,
The only solution I can come with right now is to use jQuery to strip trailing slashes (check this example: Strip Trailing Slashes), I will show you how to do it:
1.- Create a JavaScript file named untrail-nlplinks.js & save it into your theme’s root folder (where style.css is found)
Copy & paste the code below:
<script type="text/javascript">
// Once the document is ready
jQuery(document).ready(function(){
// Check links under NLPosts Wrapper
jQuery('.nlposts-wrapper').each(function(e){
// Get the content
var str = jQuery(this).html();
// Look for .html/
var regex = /(.html\/)/ig
// Replace trailing slash for .html links
var replaced_text = str.replace(regex, ".html");
// Return link
jQuery(this).html(replaced_text);
});
});
</script>
2.- Then add this to your functions.php:
wp_enqueue_script('untrail-links',get_stylesheet_directory_uri().'/untrail-nlplinks.js');
Please let me know if this works for you.
Cheers.