Facebook post images

Hello.

I hope this is not a fool question, but I have a problem when sharing a link to a blog post in Facebook.

As you know, you can get an small image and a large image, and getting a small image with text by its side is quite annoying as it doesn’t get as much engagement or clicks.

I figure some time ago that Facebook has certain aspect ratio it prefers, and that way I have been getting large images without problems, but things are not, I think, as good as they should be.

When I post a link I get a preview like this, with two images.

They are both exactly the same, but with a major difference. When I select the first one, then I get the terrible small image nobody wants:

If i select the second one, I get the big image that everybody needs.

When I share my own posts there is no problem, I select the big image and it appears as it should.
But the issue here is that, if anyone else takes a link and shares it on their pages, then by default they get the small ugly image, and I’m trying to avoid this.

When I post a link to other site I get the big image by default, and I don’t understand why my site is unable to do that.

I have different services like Yoast, The Seo Framework and currently WPSSO Core, to fix the images, crop them in the right sizes and try to get good links with big images, but they all have failed to stop the default small images when someone else shares.

It is also curious that Twitter has never given such a problem.

I don’t know if somehow my theme or some configuration or some other plugin is pushing this small image, and if someone has any idea on how to avoid it.
Or, if what I’m facing is simply normal Facebook behavior and I should only grin and bear it.

Anyhow, if somebody can help me I’ll be very grateful.

The page I need help with: [log in to see the link]