Could still be a software issue. Someone said this already but it could be possible that Lemmy.world is using a load balancer and multiple servers. These two servers' authentication tokens may be out of sync. So if you hit server 1 and you are sign in to server 1, you're good. If you hit server 2, you're signed out all of a sudden. This can also explain why the issue started to happen abruptly today. It's possible the load on the server wasn't that bad yesterday so the load balancer didn't kick in. This is all speculation. Will have to wait for an official message to confirm anything.

I love getting news from memes.

Oh wow. This looks perfect for this question. Thanks!