Delivery &1 is the wrong del. type for multiple delivery TO creation

What causes this issue?

Delivery &V1& is a posting change delivery. If you want to create
cross-delivery transfer orders, this group can only consist of outbound
deliveries.

System Response

The system has determined that the delivery you want to put in the
group is a posting change delivery.
The system does not allow you to create or enlarge a group to include
this posting change delivery.

How to fix this error?

Only assign outbound deliveries to this group.

Error message extract from SAP system. Copyright SAP SE.