Wrong Switching images between header img and featured post img

First thanks for your awesome theme. The best I could find, just I have a issue. Not sure if because I don’t know how to prevent it or it’s a bug.

So let’s say my header image is a BOOK, then my featured post image is a WOMAN, when I click on featured post image(the WOMAN), it takes me to read the whole post. And on the top of this post should stay the title post on the Featured Image(The woman), Right? Well, it appears the header image(the book). Of course with the title of the post.

Sometimes appears correct, but most of the times it comes wrong(the header image instead of the featured post image)

How do I prevent this to happen? Thanks in ahead.

Here is the example:
You can see the header image on the website: https://fiiopenminded.com/
Then you can see the second post is a Woman.
When you click the post, it comes the header image. https://fiiopenminded.com/2017/09/21/de-ce-femeile-schimba-lumea/

Ask me if I didn’t describe very well the issue. Thanks

Website: fiiopenminded.com