Error cause nginx headers

Suddenly for some days I get this error on all of the sites I run on the server:

Fehlender order nicht erwarteter HTTP response header:
server: nginx
date: Wed, 16 Mar 2016 09:44:05 GMT
content-type: text/html; charset=UTF-8
connection: close
x-powered-by: PHP/5.5.9-1ubuntu4.14
set-cookie: Array
expires: Sat, 26 Jul 1997 05:00:00 GMT
cache-control: no-store, no-cache, must-revalidate
pragma: no-cache
status: 405 Method Not Allowed
allow: GET, POST, PUT

Please bear with the problem ASAP.
Cannot backup anywhere
Andre

https://wordpress.org/plugins/backwpup/