Voice barely audible during incoming call

[Chris708]

Client with the issue is using a Yealink T46S. We are using a cloud provider Asterisk server.

I have a client in a receptionist position that has an issue where the person on the other end of the call (the caller) will hear a normal audible level of conversation for a time.
Then the caller will hear the receptionists voice go VERY faint. I have heard the same thing while troubleshooting with this receptionist.

This seems to happen when another call is coming in to her phone.

The receptionist is not using a headset, only the handset at all times.

We have swapped out phones and she still has the issue. So this rules out a specific phone issue.

There are five other phones that ring simultaneously and none of them have this issue.