I was able to reproduce the issue, it appears that my proxy app doesn’t intercept the SocketIO requests correctly. Probably it’s in the domain check (which checks if the URL needs to be rewritten) which interprets socket.io as the root domain, while it’s just a URL on the IP of the Node-RED server.
I also see another issue with an HTML file, but I’m not sure if that’s intended behaviour. I will need to check that.
I will fix the issue but it might take some time because I have to check how the dashboard loads the HTML files
