On Hook + Agent Transfer not locking ?

[eflorent]

Hi !
I'm working with 7 agent On Hook on an inbound campaign with few inbound calls.
Time to time agents have to transfer the call to another agent (also on hook).
They click transfer and manually write the extension and that works fine.
My problem is that in that case the agent can still get it's phone ringing if there is a standard inbound call.
It's seems to me that it is the actual normal behaviour of Vicidial is that true or am I missing something ?

VERSION: 2.9-441a
BUILD: 140612-1628
Asterisk 1.8.23.0-vici
2x DELL R720 - Raid 5 - 16Go RAM - Debian 7.7 Scratch Install
Dual Asterisk + MySQL 5.6.21 Master/Slave + MySQL Failover using magic IP + Dual Web DNS load balancing on Intranet + Phone Alias
Custom Agent.php, Custom Dashboard based on GoAutodial 3.3 / Custom Reporting using JasperReports Server
SIP Trunk Only (no cards, no timer clock yet) No recording
7 agents on Hook with 100 hundreds calls per days
12 agents Not On Hook with approx 2000 call per days (9 hours)

Thank you !

Best Regards

EF