Our reservation processing system has recently been updated to handle Zaui and Checkfront cancellations and rebookings. Cancelled reservations through those integrations will now remove the associated label if that label hadn't already been attached to any media at the time of the cancellation.
No configuration changes are required for clients using the Zaui and Checkfront integrations to take advantage of this change, however, ensure that your mobile devices are updated to the latest version to make sure they properly remove the deleted labels of cancelled reservations.