Look at this post https://sh.itjust.works/post/5863836

It’s just a regular image post, hosted on the instance server, but it displays as an external link, & you have to click through to view it.

Earlier, similarly formatted posts to the same community display as normal image posts.

The only difference is that the newer posts include an additional ?format=jpg parameter. I’m guessing this is throwing off the detection of an image post.