Troubles about pictures published on Facebook

Hi,
I’m using your great plugin, so I’ve some troubles about pictures.
Some times pictures are not displayed after share on facebook.
For example, when I share this link:
cal-miquel.com/offer-list/ofertas-especiales/

I don’t understand what is the order to select picture from a gallery. Some times it selects last one or others, not fisrt one, that I would like.
For example, in this link:
cal-miquel.com/all-room-list/apartamento-3-personas-terraza/

How can I fix this troubles?
Thanks a lot!

https://www.ads-software.com/plugins/simple-share-buttons-adder/