Entry of split items not possible

What causes this issue?

You have selected items and tried to generate split items. However, the
system was unable to perform this task for some items.
Split items can only be generated if the TO item has not yet been
confirmed (internally), and if one of the following conditions is
relevant for the TO item:
The TO item must be handled in batches, and the batch has not already
been entered in the item overview
The TO item refers to an administered storage location
The TO item allows packaging into handling units when confirming the
TO.

System Response

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

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.