External callers are not hearing MOH if the call goes through intercluster trunk (eg. Caller dial to UK which routes the call to another country/location via intercluster trunk).
Caller can hear the other party at far end, but when put on hold, no MOH is heard. No problem with internal calls (DN from one location calls another DN in another location via the trunk), only external calls are affected.
Unicast MOH is used.
Any advise is appreciated.