It seems that any Lemmy.world and Lemmy.ml hosted communities aren't any longer federating properly via kbin as I started getting 404 errors on all of them. Examples:
Not sure if it's the same issue, I can see new posts from lemmy but not all the comments get synced. For example I can see all the comments for the post but most of replies to those comments are missing. Also, comments made on kbin are not visible on lemmy