I use a test system for Asterisk release 220.127.116.11 with the same dialplan I use on a production system with Asterisk release 1.2.24.
The Hangup() command is not properly recognized from my Polycom phones under the 1.4 release.
After the hangup no sip channel is open anymore on the asterisk server 1.4,
but my Polycom phones still have a busy line on the phone so that I have manually end the call.
When I use eyeBeam for example, it works as expected.
Any help is really appreciated.