OK. I get it now,.
You are saying that even though the member was already on the phone, the second call coming into the group should have been delivered to the phone’s other line appearance.
The aspect of the system seeing a hangup and then sending the still ringing call (at other phones) back to the member with a new INVITE is a non-starter as he would have already had the opportunity to answer.
The above assumes that more than one line is available. BUT, I can confirm that when a second call does come in from a RG and the phone has call waiting and more than one line appearance, that indeed the phone sends a 486 and the call is never delivered to the other line appearance.
I just assumed this was how GS elected to implement the function.
As the UCM has no knowledge of the phone set-up, I assume this is perceived as a phone firmware bug?
I know of another system where you can limit the multiple call handling on phones with the capability so that while the member can use the multiple lines to their need, the system will not force another call to them if set that way. It simply looks at the extension status and if busy, moves on. If on the other hand it is not set that way at the PBX, the system level it sends the INVITE and lets the phone and user decide what to do. They do not call it call waiting, which I suspect is intended to be the same function. You can take multiple calls in that system from a RG if so desired.