An upgrade of PHP on one of our servers causes problems with the connection to session storage and you might get locked out on individual requests. Please log in with "Remember Me" enabled for now as a workaround while we work to fix the problem.
**Edit 16:48:** We managed to fix the issue for now by rolling back the upgrade. We keep investigating the underlying cause, but are quite certain that missing service restart was responsible. We apologize for the inconvenience.