WebRTC issues after internet connection hiccup

[dspaan]

One of our clients who is working on vicidial via WebRTC viciphones had an internet hiccup this morning and now when they login the viciphones still say incall but you don't hear the familiar 'you're the only person in this conference' and there is no incoming our outgoing audio anymore. I installed a softphone on of these computers and this works fine. So my conclusion was that something has to be amiss with WebRTC. I used https://test.webrtc.org but it didn't give me any clear errors.

I also used a portscan tool and port 8089 can be reached without problems. Restarting client computers and router didn't help. What other steps can i take to pinpoint what is happening here?