After upgrading and then downgrading, it looks like there might have been quirks with the cookies that were set. If you log in and it automatically logs you out, you will have to delete browser cookies for “intfiction.org” or “www.intfiction.org” or any other variations. That should clear things out, and you can log in and stay logged in. At least, that’s what worked for me.
Sorry for the inconvenience.