Open purchase order items are adjusted in the update run only

What causes this issue?

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

System Response

The changed purchase orders, in addition to other messages, can be
found in the job log. This is only possible if the reclassification
was scheduled as a background job.

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.