UCM 5.1(2) Cluster with PRI to PSTN and T1-CAS trunk to branch office PBX.
A client reported the following incident...
IP Phone Caller A makes a call to PSTN Phone X. The call progresses and completes normally.
Branch Office PBX Phone calls IP Phone A across T1-CAS trunk. Call appears to proceed and terminate normally
PSTN Phone X calls back IP Phone A and tells them they received a call, answered and heard IP Phone A's side of the conversation to the branch office phone.
I'm puzzled ... two separate circuits, two separate calls. No other reports of the same issue and can't reproduce it.
Any ideas would be GREATLY appreciated.