Getting weird issue with Nginx reverse Proxy

[blason]

Hi Team,

My portal name is lets say fs.example.com and it is configured on apache
server which is then proxied to internet using Nginx reverse proxy. However
I tried everything I was aware of and I am consistently getting below error
whenever this URL is accessed. I am running out of ideas about
troubleshooting the issue and I need a help on it. Here is Nginx config
file

```
server {
        listen 443 http2 ssl;
        server_name  fs.example.com;
        ssl_protocols  TLSv1.2;
        ssl_prefer_server_ciphers on;
        ssl_session_cache shared:SSL:10m;
        ssl_certificate           /etc/nginx/ssls/isncert/isnwild.crt;
        ssl_certificate_key   /etc/nginx/ssls/isncert/star.key;
        ssl_ciphers
'ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:E
CDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256
-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RS
A-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:
DES-CBC3-SHA:!DSS';
        ssl_dhparam /etc/ssl/dhparams2048.pem;
        ssl_session_timeout 1d;
        ssl_session_tickets off;
        ssl_stapling on;
        ssl_stapling_verify on;
        resolver 8.8.8.8 8.8.4.4 valid=300s;
        include /config/nginx/authelia.conf;
        access_log /var/log/nginx/fs/access.log;
        error_log /var/log/nginx/fs/error.log;
location / {
        client_max_body_size    10m;
        #proxy_headers_hash_max_size 512;
        proxy_headers_hash_bucket_size 128;
        proxy_busy_buffers_size 256k;
        proxy_temp_file_write_size 256k;
        proxy_buffers     4 256k;
        proxy_buffer_size  16k;
        proxy_pass http://fs.example.com;
        proxy_set_header   Host   $host;
        proxy_set_header   X-Real-IP  $remote_addr;
        proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
       add_header X-Content-Type-Options nosniff;
       add_header X-XSS-Protection "1; mode=block";
       add_header Referrer-Policy "no-referrer-when-downgrade";
       add_header Strict-Transport-Security "max-age=31536000;
includeSubDomains" always;
        include /config/nginx/auth.conf;
       include /config/nginx/restconfig.conf;
        }
}
```

And here is the error

Bad Request
Your browser sent a request that this server could not understand.

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,293780,293780#msg-293780