... [error] 10255#0: *1 upstream sent too big header while reading response header from upstream ....
Sprendimas labai paprastas, į config reikia įrašyti šias 2 eilutes:
fastcgi_buffers 16 16k;
fastcgi_buffer_size 32k;
Daugiau informacijos http://stackoverflow.com/questions/23844761/upstream-sent-too-big-header-while-reading-response-header-from-upstream
