Duplicate entry in internal table &1

What causes this issue?

An internal error occurred.

System Response

The system ignores this error are restores the status prior to
archiving.

How to fix this error?

Contact your system administrator.

Procedure for System Administrators

Please contact SAP. Duplicate entries exist in an archiving object.
These are usually due to incorrect documents. If, for example, the
header of a supplier settlement list and a document in this refer to the
same document condition, the document condition is included in the
archiving object twice. Retrieval of data is not affected by this.
The error relates to table &V1&.

Error message extract from SAP system. Copyright SAP SE.