I am not able replace gists in posts imported from Medium

In several of my archive posts, I have links to gists. On the new Hackernoon platform, they just display as the icon of my face (which is glorious, but not what users crave). In response to some tweets, I’m trying to add code examples inline or if nothing else just an image from carbon.now.sh.

However, when I go to edit the post, I get an empty editor. I don’t want to break the existing page/links, but I do want to ensure that I can fix the broken gists in the articles.

What’s the best way to go about doing this?