Problem with call transfer

I use Freepbx with centos (CentPBX)
I installed all, trunks, extensions and configured it for all that I need. The problem is with call transfer between extensions: if I tranfer a call to a people that is not speaking, it’s all ok: the line is free and the person at the other side of the phone listen the ringing signal.
If I transfer a call to a busy extension, sometimes the call ends and sometimes the people at the other side of the fone doesn’t ear nothing and close the call thinking the call crashed.
How can I resolve that?

You have unfortunately provided no real details to work with. We don’t know what version of anything you are using, type of phones, connection type, etc…

Please see:

I’m using a Centpbx Distro with FreePBX, Asterisk (Ver. 1.2.24).
I use a Ip trunx with a dsl connection and a analog line with a fxo channel.
For extensions we use Xlite. We have 9 of them.
09/09 D N 30086 OK (102 ms)
08/08 D N 8966 OK (103 ms)
07/07 D N 5060 OK (109 ms)
06/06 D N 28434 OK (102 ms)
05/05 D N 25750 OK (101 ms)
04/04 D N 36578 OK (101 ms)
03/03 D N 12160 OK (101 ms)
02/02 D N 47742 OK (101 ms)

What do you need?

a call trace showing the problem?

how can i make that? from logs or making asterisk -rvvv?

do either asterisk -rvvvvv or asterisk -r and then type set verbose 5 and capture the output displayed.

Remember to reduce the verbose logging when done or your full log will continue to capture at the higher level consuming more diskspace then previously happening.