Off-Hook and transfer to another IP Phone

[bghayad]

Hello;

vicibox 4.0.3, vicidial 2.8-404a, Build 130605-0841, asterisk 1.4.39.1-vici, Single Machine, Vtiger 5.4

With using the Off-Hook agent, and by doing Transfer - Conf using Dial With Customer or Park Customer Dial to the other IP Phone extension (the extension is 501, it is just extension within the company it self .. internally), when pressing Leave 3 Way, the button is not active (as it is dead). But if the transfer was done by Park Customer Dial, then pressing the Leave 3 way is giving affect but does not hangup. Then, if I pressed on hangup, ofcourse the call will be disconnected. But, when transferring to phone by using the DID (22288501) number which means the sip trunk will be used to reach to the IP Phone that existed in the same office, it is working fine and the surprise that once I do a one transfer for the IP Phone through its DID (22288501) which will use the provider sip trunk, then I can do transfer to the IP Phone extension 501 using Dial With Customer or Park Customer Dial and the problem disappear !

From the other side, blind transfer for the extension is working fine .. but the problem in the blind transfer that we do not know if the person is available or not and if he replied or not which will cause a problem for the customer.

Also, with On-Hook agent, this problem is not existed at all.

Is it bug? If bug, what I can do?

Regards
Bilal