NGINX Proxy picture disappears - nginx

Question

perhaps someone can help me with this issue.
I am redirecting a website over nginx with --with-http_sub_module.
So its working fine on many sites, except one picture on one of the websites.
The strange thing is that I have another Site redirected, there is a picture which is working... I have no clue for that..
Picture with chunked_encoding fehler: 59.6 kB
Picture which is working fine: 43.3 kB
I can see the picture that it is there, but only for a few milliseconds and then I get the Error: net::ERR_INCOMPLETE_CHUNKED_ENCODING
First of all my NGINX.conf:
user www-data;
worker_processes 4;
pid /var/run/nginx.pid;
events {
worker_connections 768;
# multi_accept on;
}
http {
##
# Basic Settings
##
sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
types_hash_max_size 2048;
# server_tokens off;
# server_names_hash_bucket_size 64;
# server_name_in_redirect off;
include /etc/nginx/mime.types;
default_type application/octet-stream;
##
# Logging Settings
##
access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;
##
# Gzip Settings
##
gzip on;
gzip_disable "msie6";
# gzip_vary on;
# gzip_proxied any;
# gzip_comp_level 6;
# gzip_buffers 16 8k;
# gzip_http_version 1.1;
# gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;
##
# nginx-naxsi config
##
# Uncomment it if you installed nginx-naxsi
##
#include /etc/nginx/naxsi_core.rules;
##
# nginx-passenger config
##
# Uncomment it if you installed nginx-passenger
##
#passenger_root /usr;
#passenger_ruby /usr/bin/ruby;
##
# Virtual Host Configs
##
#proxy_set_header X-Real-IP $remote_addr;
include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-enabled/*;
}
So my Proxy_config is:
{
proxy_buffering off;
proxy_buffers 8 24k;
proxy_buffer_size 2k;
proxy_http_version 1.1;
proxy_headers_hash_max_size 1024;
proxy_headers_hash_bucket_size 128;
sub_filter_types *;
access_log off;
proxy_redirect http https;
proxy_set_header Host $host;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection close;
proxy_set_header Accept-Encoding "";
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;}
Do you know something about this??
I've tried every Option from the --with-http_sub_module site, but nothing seems to work.