changeSection: Cannot send data if the connection is not in the 'Connected' State

When a supervisor tries to open up an interview from an interviewer, looking at a section “summary”, the server produces the error message “changeSection: Cannot send data if the connection is not in the ‘Connected’ State”.

What could cause this error message and how to fix it? The SurveySolutions server is the latest, running on Win Server 2019. Many thanks

Survey Solutions uses web sockets for interview details page. This message mean that client failed to connect to server. Is there a proxy server before survey solutions? Is there communication errors in dev console?

Hi Andrew, there indeed is a web socket error message that pops up. I have resolved it now.

The URL is passed through by another server that runs NGINX.
To allow for JS web sockets, I had to add the following to NGINX Conference file (maybe it is helpful to others as well):

proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_read_timeout 86400;