Raven login problems

When trying to login by going to https://gitlab.developers.cam.ac.uk/users/sign_in?redirect_to_referer=yes and clicking "Raven", I have in the last few minutes (~18:10) been taken to https://gitlab.developers.cam.ac.uk/users/auth/saml with a 404 error. As of ~18.16 I've now logged in. I was seeing this behaviour both in Firefox with an existing Raven session open, and in Chrome without an existing Raven session.