So, not sure if I am completely off base here, but I had this odd thing happen today where I couldn't post an URL because whenever I did, part of it would be replaced with the text removed. You can see what I am talking about in the screenshot, and I am linking my comment below. Another commenter replied saying it was likely...
For some reason, the link in the post I've just made appears twice: under the title (red on the screenshot), and as a link preview above the post body (blue on screenshot). All other post only have the link under the title, but no preview....