Infinite loop on sign in

Hi,

new installation on FreeBSD 12.1, behind nginx with sub url. Upon signin the screen doesn't change. In the nginx logs I see an infinite loop:

"GET /wekan/ HTTP/1.1" 200 
"GET /wekan/ HTTP/1.1" 200 
"GET /wekan/sockjs/info?cb=b6qx4vrd93 HTTP/1.1" 200 
"POST /wekan/sockjs/089/mkrfzaey/xhr HTTP/1.1" 200 
"POST /wekan/sockjs/089/mkrfzaey/xhr_send HTTP/1.1" 204 
"POST /wekan/sockjs/089/mkrfzaey/xhr_send HTTP/1.1" 204

This loops and the value after /wekan/sockjs/info?cb= changes each time. This makes me think there's an issue with the reverse proxy setup. Here's my nginx config.

    location /wekan {
        # proxy_pass http://127.0.0.1:3001/wekan;
        proxy_pass http://127.0.0.1:2000;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade; # allow websockets
        proxy_set_header Connection $connection_upgrade;
        #proxy_set_header X-Forwarded-For $remote_addr; # preserve client IP
        # this setting allows the browser to cache the application in a way compatible with Meteor
        # on every applicaiton update the name of CSS and JS file is different, so they can be cache infinitely (here: 30 days)
        # the root path (/) MUST NOT be cached
        if ($uri != '/wekan') {
            expires 30d;
        }
    }

Any ideas? Kind regards