Only outline agreements with order unit & allowed

What causes this issue?

You wish to assign an outline purchase agreement with the order unit
&V2& to the item.
However, with regard to active ingredients, only outline agreements
with the predefined order unit of the item - &V1& - can be assigned to
the item.

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?

Cancel your assignment.

Error message extract from SAP system. Copyright SAP SE.