It should only display the excerpt of each related post, in the same way an excerpt is displayed for each post in the posts archives (blog home, category pages etc).
So we can narrow down the issue, would you be able to provide us some more information…
Have you modified the theme in any way?
I ask this because it looks like you may have modified the footer.php file and I cannot see any reference to a child theme in your source code. It is always recommended to make changes in a child theme and not to change the main theme files directly.
Can you please let me know all of the active plugins on the site?
It may be that a plugin is generating excerpts for the current page/post in place of the correct excerpt for other pages/posts on the same page. Would need to know which plugins are active to rule this out.