Why WebSocket connection does not allow subpaths in URLs but HTTP polling does?

[denverFAN]

I'm running Jitsi in Docker behind a reverse proxy (NGINX). All necessary configs have been added strictly according to the documentation:

location /xmpp-websocket {
    proxy_pass https://localhost:8443;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}
location /colibri-ws {
    proxy_pass https://localhost:8443;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}

Here is my use case: I create new rooms on-the-fly by generating links to Jitsi. As my Jitsi instance serves the whole company so to prevent mixing people from different departments I usually create links according to the pattern: domain.com/DEPARTMENT/room-name. As you can see the URL contains subpath.

The problem is: If I enable WebSocket connection it always throws an error You have been disconnected once I open the link. If I disable WebSocket and return to HTTP pooling everything works fine. I crosschecked NGINX logs and everything seems to be fine - NGINX passes the request to domain.com/DEPARTMENT/xmpp-websocket?room=room-name and receives 101 code.

How can I make everything work on WebSocket exactly the same as on HTTP pooling?

I will be very grateful for any help.