IDoc file with replacement character

What causes this issue?

IDoc <(>&<)>v1& has been written in the file with at least one
replacement character.
The detailed information can be viewed in the status record of the
IDoc.

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?

It is only for information purposes.
The settings were made in the port definition for IDocs to also be
written to the file with replacement characters.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.