Problem: In this thread on community noticeboard, @NotoriousRBG reported not being able to login into their wiki, and getting persistent 502 Bad Gateway issues with the nginx web server
Reproducable? Yes, while I can access the wiki logged out and CentralAuth does auto-sign me in to the wiki, when I navigate away from the page, persistent 502 Bad Gateway issues are hit. Cannot access wiki logged in at all. To be clear, I had never accessed this wiki prior today, too.
Appears to possibly be a Varnish, nginx web server configuration, or cache problem