FI/CO interface: Currency item entered several times

What causes this issue?

Currency information was transferred several times in the current
document. The keys for the currency data must, however, be unique.
Origin of the document: &v1&, &v2&

System Response

The document could not be posted.

How to fix this error?

This is a system error of the calling application.

Error message extract from SAP system. Copyright SAP SE.