What TSP are you running? For starters you should make sure you are running TSP 8.0(2). That TSP has a handful of fixes related to transfers since TSP 8.0(1) that released with Unity 4.0(5).
One other question - does the same behavior occur if the phone is set to cfwdRNA or cfwdBusy? You might try checking the CallingSearchSpace settings on the forwarding, to make sure forwarded calls are using the CSS that contains the partition of your Unity pilot.
Other than that, I would recommend you contact TAC for help troubleshooting where the call is getting dropped.