Serialization: A more recent IDoc has already been processed

What causes this issue?

During processing of an IDoc for a condition change, the system found
that a more recent version of the condition change had already been
processed. In the communication layer, one document can be 'overtaken'
by another if the line is busy and the communication program therefore
switches to another line.

How to fix this error?

The IDoc cannot be imported as it does not contain up-to-date data.

Error message extract from SAP system. Copyright SAP SE.