When a call forwarding will be disabled or if user will do any changes the change will be updated to the network but not to the UI. So when any change will be done to the call forwarding all information should be updated from network.
An other issue with call forwarding is that when you activate the call forwarding for all calls (CFU) the other call forwardings is not shown on the list. Ofcourse it's overrides the other CFs but those are still defined on VLR and the numbers should be shown also in the list.
Third thing is that it would be nice that in the lock screen were shown an indicator for the CFU.