Call queue Skip Busy Agents Aastra 9133 Phone - Get next call when putting call on hold

We are utilizing call queues and have the option Skip Busy Agents turned on.

When a call is answered from the queue from an Aastra 9133i phone and then transferred, which puts the call on hold as you anounce the transfer, another call fron the queue starts ringing on line 2.

This does not appear to happen when using a softphone. Any ideas would be greatly! appriciated.

Distro: CentOS 5.2
Kernel: 2.6.28 - 32 bit
Asterisk version: 1.4.24
Queue Module: 4.6
Aastra Model: 9133i
Aastra phones firmware: