I keep getting this error when I try to click notifications, inbox, bookmarks, or account options. Yesterday when it started I would also randomly get it while typing instead of the "Draft saved" message.
Its intermittent, and I haven't seen a pattern to it yet. It usually seems to clear up if I change pages a few times, but sometimes while I'm getting it I'll also start getting this, which sometimes leads to me appearing to be logged out (but not actually being logged out).
Error 503 Service Unavailable
Varnish cache server