At least one HU cannot be assigned to the delivery

What causes this issue?

You want to include HUs in a delivery. At least one of the selected HUs
contains an item that does not correspond to the delivery item in the
characteristics material, batch or storage location.

System Response

Enhancing the delivery is possible under certain conditions.
For JIT and in conjuction with Full-WM-managed storage location, it is
in principle impossible to enhance deliveries.

How to fix this error?

Call transaction VL10HU, and activate the indicator Increase Delivery
Quantity in the user role Deliver Handling Units. In so doing, a new
item can be included in the delivery, or if the criteria for adding to
the delivery are not suitable, an additional delivery can be created for
this item.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.