I just realized that the related post feature is not working properly in my posts.
The post supposed to show related posts in the bottom of the post body, but sometimes it shows a post that is not related to it, sometimes it shows one of the various posts that I have related to it and sometimes it shows nothing.
Note that all the posts I’m referring to has the same category. I even inserted the category “no category” to test. But the result is the same.