I made a post on WordPress, then shared it on a Facebook page. In the past, the shared image would be the large "post" image. But now, for some reason, it's using the thumbnail. Running the url through fb's debugger shows that Open Graph recognizes both og:images, but that neither of them are being used in the share preview. Once posted, it uses the thumbnail.
I checked the meta content in the page head just to double check and sure enough, it looks fine:
<meta property="og:image" content="##">
What's causing this? It's recognized, but not used. What?
I currently facing the same issue, after contacting facebook, it turns out there is an issue in Open Graph in facebook that affects some users.
The Bug has been reported and assigned as "high priority" in Facebook support center - https://developers.facebook.com/bugs/978421888869140/