Channel Spy Problem

We recently implement 1.4.21.

We have setup of 100 agents using sip trunk.

We are using channel_Spy application for barge in agent desk.

When using channel_spy application, its working fine until agent put customer on hold. When agent unhold the customer, we are unable to listen customer voice ( unable to get customer channel ). And if call disconnected by Customer during hold, it jumps to any uneven channel for spying.

I started with 1.4.19 and still this problem facing in 1.4.21.

Is there any solution for the same???