W79P - caller can't hear us

[sgbarrow]

I have about 50 W79P installed in my restaurants. We have had at least 10 issues where the guest cannot hear my employee on the phone. The issue seems to come and go. Is there a known issue with this phone? We have tried all of the troubleshooting from re-registering the base station, factory reset, insuring proximity to the base station, volume settings, ringer settings, etc. RingCentral tech support cannot help us. They simply tell us to factory reset and replace the phone if that doesn't work. I have replaced at least 7 phones in the past year so I need to find a fix here. Any suggestions? Thanks

Best,
Steve