Document found via restart

What causes this issue?

The billing document could not be created when the processing step was
first executed. A restart of the processing step was executed.
During this process, the system determined that this claim had already
been billed. A new billing document was not created. The number of the
billing document was taken from the document flow.
No further messages have been logged for this reason.
The processing step restart took place on &V1& at &V2&.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

System Response

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.