We recently upgraded a very old server from Asterisk 1.8 to 18.9
and we are having a strange issue with calls in queues.  We use Queuemetrics to manage our agents and extensions are configured as Local/XXXX@from-queue/n to connect clients to agents.  This is because if you dial PJSIP/XXXX directly it will only call the first registered device for that extension and not all of them.  The problem we are facing is that sometimes there is no audio on the call coming from the queues.  Most of the time everything is fine and it is very random when audio does not flow.  I have tried to debug SIP but I do not see anything wrong and audio should be flowing, it can take a long time between failures so it is very difficult to catch the correct call.

    I have another pbx using the same setup with Asterisk and Queuemetrics, only difference is that it uses Asterisk 18.5 and we do not have any problems with audio there.  As far as I know only calls from the queues have this issue, direct calls to the extensions or outgoing calls do not.  Could this be an issue with the Local channel? 
I use the /n because that is the example published in the Queuemetrics documentation.  I do not know if removing it will affect the call.  Any recommendations to properly debug this issue?

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Telecomunicaciones Abiertas de México S.A. de C.V. Carlos Chávez
+52 (55)8116-9161

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