I don't know the call volume on your system or if you have any quiet times, but maybe it just needs to be properly shut down and restarted, and then it will magically work again after that.
One other thing you could check, which should happen automatically in the early AM hours, is to go into Configuration Manangement - Network - System, and then hit the Search button so the data comes up. Make sure that everything says Synchronous, which means all of your memory, software and hardware databases are in sync. If any of the items does not say Synchronous then you can press the Synchronize button and everything should normalize again.
*** NOTE - I would not do that during any kind of busy time because it does put a load on the system and can temporarily affect some of the features.
See if that helps any.