Capture active call from queue when trying to pickup a new one

General Help
1

Scenario:

  • a FreePbx 2.7 system with one Queue number 60, several extension belonging to the Queue in linear order;
  • Asterisk 1.6.2.9;
  • incoming calls are routed to the Queue;
  • in /etc/asterisk/extensions_custom.conf I have defined 8 as a Pickup code only for incoming calls thru Queue: exten => 8,1,Pickup(60@ext-queues)

This is the normal behaviour:
External caller Alice calls in, extension A starts ringing.
Ext A picks up the phone and answer Alice.
While Alice and A are still talking, Bob calls in, extension B starts ringing.
Extension C use code 8 to pickup the call and answers to Bob, while B stops ringing.

Now, this is the strage part:
External caller Alice calls in, extension A starts ringing.
Ext A picks up the phone and answer Alice then transfer the call to ext B.
While Alice and B are still talking, Bob calls in, extension A starts ringing.
Extension C use code 8 to pickup the call but instead of answering Bob, he is put is conversation with Alice, B is disconnected back to idle state, and Bob’s call is still waiting to be answered.

Any suggestion on that?

2