An internal error occurred (see long text)

What causes this issue?

An internal error occurred as the system read a document from the
archive.

System Response

The document was not read. Processing cannot continue.

How to fix this error?

INCLUDE ISR_VERWALTUNG

Procedure for System Administrators

Contact SAP. The error relates to function module "wlf_generate_index".
The system expects a header document when it reads a data record using
function module "archive_get_next_record".

Error message extract from SAP system. Copyright SAP SE.