GS1200-8 Webinterface behind nginx reverse proxy

I'm running a local nginx reverse proxy as gateway between my home network and the management network. The switch webinterface is reachable from the management network, the Idea is to use nginx to have secure access to the switches webinterface from the home network.

This is my nginx config:

#/etc/nginx/conf.d/switch.conf;
server {
    listen 80;
    listen [::]:80;
    server_name switch.lan;

    # Enforce HTTPS
    return 301 https://$server_name$request_uri;
}

server {
    listen 443 ssl;
    listen [::]:443 ssl;

    server_name switch.lan;

    include /etc/nginx/ssl.conf;
    auth_basic           	"Restricted Access!";
    auth_basic_user_file 	/etc/nginx/.htpasswd; 

    client_max_body_size 0;

    location / {
        proxy_pass http://192.168.10.10;
        include /etc/nginx/proxy.conf;
    }

    ssl_certificate /etc/nginx/cert.pem;
    ssl_certificate_key /etc/nginx/key.pem; 
}

#/etc/nginx/proxy.conf;

# Timeout if the real server is dead
proxy_next_upstream error timeout invalid_header http_500 http_502 http_503;

# Proxy Connection Settings
proxy_buffers 32 4k;
proxy_connect_timeout 240;
proxy_headers_hash_bucket_size 128;
proxy_headers_hash_max_size 1024;
proxy_http_version 1.1;
proxy_read_timeout 240;
proxy_redirect  http://  $scheme://;
proxy_send_timeout 240;

# Proxy Cache and Cookie Settings
proxy_cache_bypass $cookie_session;
#proxy_cookie_path / "/; Secure"; # enable at your own risk, may break certain apps
proxy_no_cache $cookie_session;

# Proxy Header Settings
proxy_set_header Connection $connection_upgrade;
#proxy_set_header Early-Data $ssl_early_data;
proxy_set_header Host $host;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Proto https;
proxy_set_header X-Forwarded-Ssl on;
proxy_set_header X-Real-IP $remote_addr;

I can get to the login screen, but after entering the password, I'm redircted to https://switch.lan/login.cgi which looks like this:

When entering the password again I'll get this message:
"If a user is logged in already, other users will not be able to access the webpage."

The nginx error.log is empty. I guess some redirect gets lost, perhabs you guys know what I'm missing.

Cheers