T48G - Incoming call during attended transfer

[gspiliot]

I have bought three T48G for a customer. I am using the latest version of the firmware and I have a very specific problem during attended transfers. Call waiting during a call works as expected, no problems at all. I have a problem with the following scenario:

Call comes in, the secretary answers. She decides to do an attended transfer. She presses the "transfer" key and then the BLF of the extension. The extension starts to ring. Everything is normal till now. Then before the extension has the opportunity to pick up the (attended transfer) call another call comes in to the secretary's phone. Instead of a subtle beeping tone and a display notification the attended transfer call is stopped and the main entry on the phone's screen in the new incoming call.

Why should the current attended transfer connection gets disrupted by a new incoming call?

Thanks
George.