Problem with wrong comments displaying

Hello,

I want to add a related posts list to my posts without use of a plug-in. I used the second code snippet at this site to show related posts based on tags:

https://www.awesomewordpresstheme.com/display-related-post-in-wordpress-without-plugin.html

And placed it in between the post content and the comments. It’s working well, EXCEPT: Now the comments for the post, which appear below the related posts list, are wrong. In fact the same comments appear for all posts–the theme has lost the ability to know which comments go with the post.

Any thoughts?

Thanks,

–Harry