Owncloud download fail behind reverse proxy

I have raspberry pi with nginx as reverse proxy and another machine with owncloud on nginx too.

I can connect and browse in the pages but when I try to download a file that weight more than about 50mo, the download start a bit and fails.

I know the problem come from the reverse proxy, because if I access owncloud directly (locally), downloads work.

owncloud vhost :

server {
    listen 80;
    server_name cloud.spooky4672.me;
    return 301 https://$server_name$request_uri;
}

server {
    listen 443 ssl;
    server_name cloud.spooky4672.me;

    #SSL
    ssl_certificate /etc/nginx/ssl/cloud/cloud.spooky4672_chain.pem;
    ssl_certificate_key /etc/nginx/ssl/cloud/key.pem;

    #LOGS
    access_log off;
    error_log /var/log/nginx/owncloud-error.log;

    location / {
            proxy_pass http://local_ip;
    }
}

proxy.conf

    proxy_redirect          off;
    proxy_set_header        Host            $host;
    proxy_set_header        X-Real-IP       $remote_addr;
    proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
    client_max_body_size    10m;
    client_body_buffer_size 128k;
    client_header_buffer_size 64k;
    proxy_connect_timeout   90;
    proxy_send_timeout      90;
    proxy_read_timeout      90;
    proxy_buffer_size   16k;
    proxy_buffers       32   16k;
    proxy_busy_buffers_size 64k;