We are using CM 3.1.2 with an 8720 server in 1 location and 8500 server in remote location as ESS. When a Supervisor located in Main(8720) uses SO feature to observe an agent located in remote ESS(8500) the call will sporadically go silent after the agent places the caller on hold and won't restore until the next call. The two sites are interconnected via LAN and TIE trunks using 2420 digital sets. Has anyone else seen this or have any idea what might be causing the issue?