Posting to any lemmy.world community with a lemmy.sdf.org-hosted image as URL results in the post never shows up

For example, I created this post with this image hosted on lemmy.sdf.org as URL. The post never made it to !skiing@lemmy.world.

However, the same post with the same image hosted on pixelfed.sdf.org made it just fine.

This is just one example. I've made at least a dozen such posts and each time this happens without fail - unless the URL is something other than a lemmy.sdf.org-hosted image.

Not sure where to report this...