When they try to do this they may be presented with something similar to the below:
Lines can only be removed from a Shipment when the Shipment is at Due Out.
Once it goes past Due Out, for trace-ability purposes Lines can't be taken off a Shipment.
Cutoff can be set however if you wish to ignore this lines and get the shipment out.
Please note Cutoff should only be pressed if all other stock required has been picked.