If you bring up the Devices list and see one of your devices listed twice, there is a simple solution. This should only happen if you have disconnected a device and selected the "Remember" option, then reconnected the same device later to a different input port.
The devices will be in order of the ports they are connected to, so you should be able to determine which is not connected so you can delete it by seeing which ports on Control Center are being used.
To delete the duplicate entry, go to Settings> Devices> and choose the appropriate entry, then "Forget device".
