Forwarding internally gives "missed call"

[Kurt2]

We run 3CX (Ubuntu iso). Latest V18. Alle deskphones are latest firmware.

When there is an external call and userA takes that call there is no problem.
But then userA wants to forward to userB.
UserB hears the phone ringing. He takes the call.
Then userA puts down the earphone.
UserB doesn't hear the caller. Then userB put down the earphone and then the phones rings again.
When userB takes that call he hears the caller.
When userB closes the call he has a missed call from userA.

How can we solve this? It is like there is a serious delay, but all phones are on the same pbx.

Thanks in advance.
Kurt

 

[TheodorosG_3CX]

First of all 3CX ISO is not an Ubuntu but a Debian installation. You should use the 3CX ISO otherwise the PBX is under an unsupported environment.
From the description though i understand that you do not press transfer.