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:
https://lemmy.world/c/personalfinance: ok
https://kbin.social/m/personalfinance@lemmy.world: 404
https://lemmy.ml/c/fire: ok
https://kbin.social/m/finance@lemmy.ml: 404
https://beehaw.org/c/finance: ok
https://kbin.social/m/finance@beehaw.org: ok
You still see content, just not any new content from that instance from the moment it updated to 0.18, except content made by users who are on other instances that not yet have updated.
I’m browsing /newest and seeing posts from lemmy.world. The time that OP says the magazine was created on this instance matches when I did my search. I really don’t think the 0.18 thing is what OP is running into (lemmy.world is running 0.18.1-rc.7).