Recently the featured images stopped displaying when shared on Facebook - is this what you are referring to? I even grabbed an older Constant Contact link that displayed fine, reposted it, and it is displaying the same error.
I'm not seeing the post that you're referring to, but what you're describing is something we've seen as well in some cases. Generally it seems to be based on the original image size. When posting to Facebook, it's best to use images that are 200x200 pixels or 475x247 pixels. Any image smaller than 200x200 pixels will automatically be rejected. We've noticed that images with large amounts of text can sometimes be removed automatically as well, and in rare instances other content can trigger their image filters. These restrictions weren't always in place on their side, so that could be why you're seeing problems with old posts, that worked fine before their image policy changes.