Room fills up with Ghost calls

We have rooms with ‘ghost channels’ - the room fills up with callers that have left the room
but their signal still remains the room, eventually maxing out and crash. Essentially, the room becomes
dead - no sound call be heard in the room. The room becomes functionless. Eventually, we have to reboot
the entire system to reset the room. This issue also occurs when callers press * repeatedly. It causes the room
to fill up with ghost calls or channels.