Diagnosis
You tried to assign an HU to a delivery which has already been reservedfor a different delivery. The shipping labels have already been printedaccordingly.

Procedure
You can nevertheless assign the HU to the delivery by using the packingfunction in the delivery. However, output control will not issue anotification. If you want to receive a notification for HUs that arereserved for the delivery, you have to change the reservation of the HU.