Tried alpha4 and now alpha5 (from dsring) and it still giving me the same thing. I can roll back to 55 and everything works fine.
Maybe if someone could roll a version of the firmware without the updated web server changes? I know nothing for firmware development but my guess is maybe something broke with those fixes.
A lot of the firmware backend code lives in the httpd. You can't just use previous versions, it will break various features such as the network map, and a lot of code in it has changed since the last release - including numerous security fixes.