You would need to look at the console logs when the error occurs and see what may be causing it, but it sounds like another application is taking over the microphone. I would setup a sound profile for the headset they are using and have them not use other applications that might use the microphone at the same time with GC.
------------------------------
Robert Wakefield-Carl
Avtex Solutions, LLC
Contact Center Innovation Architect
robertwc@avtex.comhttps://www.Avtex.comhttps://RobertWC.Blogspot.com------------------------------