Cross-company postings not permitted for document type &1

What causes this issue?

This document contains line items with different affiliated companies.
The specifications for an affiliated company will still be seen as
different if a company number is given in one open item but not
another.
For document type &V1&, the Customizing setting requires that the
affiliated company be unique.

System Response

Error message; you cannot post the document.
INCLUDE FICA_NA_CUST OBJECT DOKU ID TX LANGUAGE EN

Error message extract from SAP system. Copyright SAP SE.