Batch & for material & had vendor batch &

What causes this issue?

In the batch master record, batch &V1& of material &V2& already has
vendor batch &V3&.
However, when the PO was placed, a different vendor batch was assigned
to the batch.

System Response

Depending on the system configuration, this message is either a warning
or an error message.

How to fix this error?

<ZH>Error message:</>
The vendor batch in the batch master record and the vendor batch in the
purchase order must be the same. Terminate current processing and
change the vendor batch as follows:
Change the vendor batch in the batch master record.
Change the vendor batch in the purchase order by changing the batch on
the detail screen of the PO item.
<ZH>Warning message:</>
If you still post the item with the vendor batch, the system overwrites
the vendor batch in the batch master record with the new vendor batch.

Error message extract from SAP system. Copyright SAP SE.