Firefox? I've seen FF occasionally cache broken headers very aggressively. Can sometimes fix by opening the history view (ctrl+H for many OS's), finding the URL in question, right-click and "forget about this site."
(Image is working for me on FF38 w/disconnect and ublock)
(no subject)
Date: 2015-06-23 06:44 pm (UTC)(Image is working for me on FF38 w/disconnect and ublock)