I would like to add a few details on the above described problem. I added one more post, and what happens is that it appears twice, but the first post now appears normally only once.
So, to better describe the issue, the last blog post appears twice.
Also, I noticed that the “continue reading” button of the top appearing copy of the duplicated post, links to the blog page (which does nothing, it’s the current page). The same button of the same post just below, works perfectly, as it links to the page of the article.
Similarly, the social media icons of the top appearing post, share the blog page (generally, not the article it is supposed to share). And the same social media buttons, on the same post which appears below, work fine, as they share normally the specific post, as it should.
So, what I need is to get rid of the top appearing blog post, which is a duplicate of the last published post and doesn’t work properly.
Other than this, everything works fine and it is a great plugin!