Signing in with Google sticks, and an expired session says so

A member reported that Continue with Google kept returning them to the login page. Google and our servers were working every time; the problem was an old sign-in token the browser had kept from an expired session. It was sent with every request and took priority over the fresh sign-in Google had just completed, so the site asked "who is this?" with the dead token and was told nobody. Each new attempt created another valid session hidden the same way. A dead token is now cleared the moment it fails, and the fresh sign-in is used.

A related fault could leave you looking at your own account, signed in as far as the page was concerned, while every change you made was refused. It landed hardest on account deletion: a member trying to delete their account was repeatedly told their session had expired, and eventually wrote in to ask us to do it by hand. When the server has proven a session is dead, the page now clears it and asks you to sign in again, instead of showing you an account that cannot save anything.

One more thing, for anyone not signed in: pages now show the Login / Join Us buttons straight away rather than a loading placeholder that turned into them a moment later.