Delivery group & is not complete

Message type: E = Error

Message class: VL -

Message number: 089

Message text: Delivery group & is not complete



What causes this issue?

<GL:delivery_group>Delivery group</> &V1& copied from the sales order
on which the delivery is based, is not complete. Not all items of the
delivery group exist in this delivery.

Error message extract from SAP system. Copyright SAP SE.