The Mediation Server service has encountered a major call completion problem with the Front End. Front End FQDN: %1 Cause: ...

Lync Server 2013

The Mediation Server service has encountered a major call completion problem with the Front End.

Front End FQDN: %1
Cause: Calls to this Front End failed 5 times with failure final responses.  Check other MOM alerts for more details.
Resolution:
If the failure is due to CALL_FAILURES_DUE_TO_UNEXPECTED_PROXY_INTERACTION, there is some internal issue with the Front End's link to the Mediation Server (misconfiguration, load) that is causing it not to complete calls.  Please consult the failure reports on the Monitoring Server for more details.

The Mediation Server can be collocated on a Front End pool. Collocation requires fewer computers, but in larger deployments ... The Mediation Server service definition is removed from topology configuration. The service will be running using the old ... The Mediation Server service failed a call because of too little bandwidth available on the Front End leg of a call. The ... The Mediation Server service failed a call because of too little bandwidth available on the Trunk leg of a call. The Mediation ... The Mediation Server service has encountered a major call completion problem with the Front End. Front End FQDN: %1 Cause: ... The Mediation Server service has encountered a major call completion problem with these Trunk peer(s). Affected PSTN Trunk ... The Mediation Server service has encountered a major connectivity problem with the Front End. Front End FQDN: %1 Cause: ... The Mediation Server service has encountered a major connectivity problem with these Trunk peer(s). Affected PSTN Trunk Service ... The Mediation Server service has encountered a major internal problem that may be causing it to fail calls. Cause: Check ...