Facebook noticed some irregularities with the image associated with this message, but it will not prevent the message from sending. However, the preview you currently see may be different than when the message is published. To resolve this issue, you do not have to do anything. We will try to rescrape the image and the situation should resolve itself.
Why did I receive this error?
This error happens on Facebook link-type messages when the scrape finds images associated with the link, but the message did not have an image associated with it. This can happen because the link is being scraped for the first time by Facebook's systems. There is just a small delay as we to try to accomodate the speed of your website and give facebook time to scrape and cache the image so your link will post with a proper preview.
What should I do to resolve this?
The message will eventually be sent even if this error happens because it is more of a check than an actual failure.
How do I prevent this error from happening in the future?
You can start as an image-type message and upload an image and then switch to link-type.