WebRTC audio is blank on Ubuntu 17.10 using Chrome

Ubuntu Desktop OS ver 17.10
Chrome Browser ver 65.0.3325.181
Firewall: Cyberoam

We are providing VoIP using WebRTC for our clients. So typically our clients would login using Chrome web browser and the webrtc engine will be started. Thus allowing our clients to establish VoIP connection to our cloud server without any additional software to be installed.

We have clients using Ubuntu and Chrome Browser (versions same as above). However we stumbled upon a client where we are experiencing blank audio on calls. Initially we doubted it could be due to firewall, however when we checked our webrtc application on a windows machine on the same client network, there is no problem with blank audio whenever we tested.

Strangely the issue happens only on Ubuntu OS and it happens randomly as there is no specific time pattern when the issue would occur. What really surprised us is that we didn’t encounter this blank audio issue one whole day on both Ubuntu and Windows systems. That was only once and then the problem started again on Ubuntu systems.

Let me summarize the above:

*WebRTC based VoIP application works on Windows everytime
*Windows and Ubuntu systems are on same network under Cyberoam firewall
*Only Ubuntu has random problem with blank audio

Any help to this problem is much appreciated.