I have discovered the consultative call transfer problem. The consultative call transfer problem occurs with 12.4(20)T2, which is in the 7.0.2 and 7.0.3 releases, but does not occur with the 12.4(22)YB1, which is in the 7.1.1 early adopter release, or the 12.4(11)XW releases (which are included in the 4.2.x releases). I have seen similar call transfer problems reported by other UC520 users in the Cisco Community Central forums.
Will there be a updated software pack for the UC520 that fixes this problem? This problem does not appear in the 7.1.1 early adopter software pack, which includes the IOS 12.4(22)YB1 release.
One workaround for the consultative call-transfer problem is to do the following:
The above commands disables consultative transfer and only performs blind transfers.