WebRTC - WebRTC: ICE failed, add a STUN server and see about:webrtc for more details

I am trying to stream a video to a browser using WebRTC. The error I am receiving is WebRTC: ICE failed, add a STUN server and see about:webrtc for more details. This is a bit surprising to me because in my code I am mentioning one of googles STUN servers in the config-object for the peer connection like this:

const config = {
        iceServers: [
          {
            urls: ['stun:stun.l.google.com:19302']
          }
        ]
      };

I already tested this on the PC, the project is running on and was able to see the stream there. Now I wanted to access the website over an ssh tunnel. I forwarded the port and can now open localhost:4000 in the browser and see the website however the video won't show up and I'll get the described error.

How can I stream the video also to the remote PC or why is it not working over the ssh tunnel? Thanks in advance!