I have a Cisco SPA8000 currently connected to an Office IP500 providing analog lines to the system. I am having an issue where conference call lines are not able to be properly dropped. When I try to drop the call the lines get stuck and I need to reboot the system or ATA to make the lines clear. If I have a single line on the phone the drop works fine it is only when I do the conference call does this occur. Anyone have any suggestions?