Settings for subledger transfer are not consistent (contract accounts)

What causes this issue?

The settings for transfer to another subledger differ. The document
cannot be posted.
The document contains items on different contract accounts for which the
transfer application has not been maintained consistently.
The contract accounts affected are &V1& and &V2&.
Since a document can only be transferred in full with all items and the
settings for transfer have to be identical for all items, it is not
possible for the document to be posted in this state.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.