How to fix broken calls in Lync?

Question

FreeSWITCH

Hello.
There is a server with win 2012r2, Lync server 2013 is installed, freeswitch is installed on the same host. Freeswitch + Lync is configured according to the article on Habré "PSTN gateway for Lync Server based on FreeSWITCH"
The essence of the problem is that when calling from Lync clients, the connection is disconnected spontaneously. I called the provider, took a dump, says fs sends packets normally and then sends by. Restarting the "Lync Server Mediation" service (C:\Program Files\Microsoft Lync Server 2013\Mediation Server\MediationServerSvc.exe") helps to partially solve the problem. You may not observe the problem for a couple of days, then it occurs.
Tell me where to look.