Seafile server in fast-cgi mode + SSL + Nginx : working but sometime errors found in logs

Hi everyone,
I run Seafile server 6.1.12 on an small ARM platform (Orange Pi Zero)
Seahub is started in fast-cgi mode. I use SSL encryption and nginx as server.

Everything seems be OK at first glance : Seafile client synchronize well, I can access the Web interface. However, when I try to download a relatively large file (>10MB) from the Web access, the download fails a few secondes after the beginning.

I find errors in /var/log/nginx/seahub.error.log :

2017/10/12 14:49:18 [error] 587#0: *2004 recv() failed (104: Connection reset by peer) while reading response header from upstream, client: A.B.C.D, server: myserver.ddns.net, request: “GET /thumbnail/… HTTP/1.1”, upstream: “fastcgi://127.0.0.1:8000”, host: “myserver.ddns.net:8001”, referrer: “https://myserver.ddns.net:8001/

2017/10/12 14:49:20 [error] 588#0: *2006 recv() failed (104: Connection reset by peer) while reading response header from upstream, client: A.B.C.D, server: myserver.ddns.net, request: “GET /thumbnail/… HTTP/1.1”, upstream: “fastcgi://127.0.0.1:8000”, host: “myserver.ddns.net:8001”, referrer: “https://myserver.ddns.net:8001/

2017/10/12 14:51:05 [error] 590#0: *2209 upstream timed out (110: Connection timed out) while reading response header from upstream, client: A.B.C.D, server: myserver.ddns.net, request: “GET /api2/account/info/ HTTP/1.1”, upstream: “fastcgi://127.0.0.1:8000”, host: “myserver.ddns.net:8001

2017/10/12 14:52:02 [error] 588#0: *2220 upstream timed out (110: Connection timed out) while reading response header from upstream, client: A.B.C.D, server: myserver.ddns.net, request: “GET /api/v2.1/notifications/?_=1507812481712 HTTP/1.1”, upstream: “fastcgi://127.0.0.1:8000”, host: “myserver.ddns.net:8001”, referrer: “https://myserver.ddns.net:8001/

2017/10/12 22:35:32 [error] 587#0: *2414 recv() failed (104: Connection reset by peer) while reading response header from upstream, client: A.B.C.D, server: myserver.ddns.net, request: “GET /api2/repos/… HTTP/1.1”, upstream: “fastcgi://127.0.0.1:8000”, host: “myserver.ddns.net:8001

Here is my nginx config file :

user www-data;
worker_processes 4;
pid /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;

	##
	# SSL Settings
	##

	ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE
	ssl_prefer_server_ciphers on;

	##
	# Logging Settings
	##

	access_log /dev/null;
	error_log /dev/null;

	##
	# 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/javascript text/xml application/xml application/xml+rss text/javascript;

	##
	# Virtual Host Configs
	##

	include /etc/nginx/conf.d/*.conf;
	include /etc/nginx/sites-enabled/*;
}

Here is seahub.conf :

server {
    listen 8001; # <--------------------------------------- NGINX PORT
    ssl on; # <-------------------------------------------- SSL
    #ssl_certificate /etc/nginx/ssl/seahub.crt; # <--------- SSL
    #ssl_certificate_key /etc/nginx/ssl/seahub.key; # <----- SSL
    ssl_certificate /etc/letsencrypt/live/myserver.ddns.net/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/myserver.ddns.net/privkey.pem;
    server_name myserver.ddns.net; # <----------------- CHANGE THIS
    error_page 497  https://$host:$server_port$request_uri;

    location / {
        fastcgi_pass    127.0.0.1:8000;
        fastcgi_param   SCRIPT_FILENAME     $document_root$fastcgi_script_name;
        fastcgi_param   PATH_INFO           $fastcgi_script_name;

        fastcgi_param   SERVER_PROTOCOL $server_protocol;
        fastcgi_param   QUERY_STRING        $query_string;
        fastcgi_param   REQUEST_METHOD      $request_method;
        fastcgi_param   CONTENT_TYPE        $content_type;
        fastcgi_param   CONTENT_LENGTH      $content_length;
        fastcgi_param   SERVER_ADDR         $server_addr;
        fastcgi_param   SERVER_PORT         $server_port;
        fastcgi_param   SERVER_NAME         $server_name;
        fastcgi_param   HTTPS   on;
        fastcgi_param HTTP_SCHEME https;

        access_log      /dev/null;
        error_log       /var/log/nginx/seahub.error.log;
    }
    location /seafhttp {
        rewrite ^/seafhttp(.*)$ $1 break;
        proxy_pass http://127.0.0.1:8082;
        client_max_body_size 0;
    }

    location /media {
        root /home/seafile/seafile-server-latest/seahub; # <-- change: 2014-07-11
       # include /etc/nginx/mime.types; # <--- UNCOMMENT THIS IF CSS FILES AREN'T LOADED
    }

    location '/.well-known/acme-challenge' {
        default_type "text/plain";
        root /home/seafile/certbot-webroot;
    }

}

Do you have an idea ?

Regards,

Damien