Not all posts being synced to Lemmy.ca?

So if I look at a community's page on the instance proper, like: https://lemmy.ml/c/artificial_intel . There are posts there that are not reflected when I look at it from lemmy.ca: https://lemmy.ca/c/artificial_intel@lemmy.ml Including a post that I've posted from Lemmy.ca!

Is there something I'm misunderstanding about federation that would lead to this behaviour?