This could be happening with other instances but I've only seen it with lw. Occasionally I'll make posts into lemmy.world communities that just don't federate. It's not delayed federation -- the post always exists in that community but only on the copy of it here and only Lemmy.ca users can see it and interact with it. It's kinda like a secret Canadian version of the community, I guess.

It's more of an inconvenience because it happens fairly infrequently but is this a known problem? Is it resolvable?

Edit: this just happened with the last story I posted to c/world. When it wasn't on the actual l.w page, I deleted it, reposted it, and it worked fine. In the past though, there have been stretches of up to a few hours where nothing makes it off the server.