in our environment we have a CCM 4.1 with IP Phone 7940. Sometime a transfer call drop and the target phone reset. In detailed:
Phone A received a call --> Phone A make a transfer w/ consult call to Phone B --> Phone B respond and talk with A --> Phone A complete the transfer --> Phone B drop the call, display a "CM Inactive" message and reset.
The issue is episodic. The telephone B is remote but the network connection is always ok.