Loss of sound in calls from asterisk?

Question

Asterisk

The situation is the following. There is a server with Asterisk 11.18.0. The gsm gateway Openvox is connected to it. Also, 3 internal subscribers have been created, each of which has a SIM card attached to the gateway. The situation is as follows, the manager calls (or the manager is called), the conversation begins. Everyone hears each other well. But lately, the sound has been dropping out more and more. That is, the conversation is not interrupted, but simply the subscriber and the manager do not hear each other. And it doesn't always happen. Tell me, how can I track why the sound disappears on both sides? Do you have any guesses as to what it might be?
Here is the debug of the call that caused the sound to disappear
asteriskforum.ru/viewtopic.php?p=80894#80894

Answer 1

Well, for starters, it would be nice to dump such a call and see what's going on with RTP.
Then you can openVox to see the signal strength and reception quality for a specific sim card.

Answer 2

The problem with the sound is almost always plugging with RTP, see if the RTP port ranges on the aster, on the telephone set and on the GSM gateway match. The symptoms you describe are similar to trying to change the RTP stream