I am experiencing inconsistent behavior that just changed this week although I did not apply any changes on my side.
Old blog posts: Facebook and LinkedIn both resolve the URL to show the blog post excerpt and image in both the preview and after shared. This still works with new shares of old posts. (e.g. old post)
New blog posts: Facebook works, but LinkedIn does not. On LinkedIn, it just shows the domain part of the URL and that is it. (e.g. new post)
The only thing I can think of that is different is that it was a different contributor that uploaded the text content. But I am the one who uploads photos and actually publishes the posts.