Intermittent Dead Air Calls with Voice Notification

Ignition 7.9.10
I have a customer using a Grandstream HT813 on a dedicated land line for voice notifications. For the most part the notifications are working just fine. Occasionally a call will be answered and there is just dead air. After hanging up, the call repeats and again dead air. Even tried pressing any key to continue like a normal call to get the alarm message still leaves just dead air. It seems to be very random and not alarm specific.

I triggered a built in test alarm to my admin pipeline multiple times sometimes answering immediately, sometimes ignoring the 1st or 2nd call, sometimes hanging up mid call. Every single one worked correctly with no dead air calls.

My guess is that it is something in the Grandstream HT813 that is not passing the message from Ignition, but not sure what to look for or try. Anyone have any thoughts or ideas? Thanks!

I’d start by looking in the gateway logs for odd error messages that correspond to the time of those dead air calls…