EDI: Syntax error in IDoc (mandatory segment missing)

What causes this issue?

The segment &v3& has the attribute 'Mandatory' in the syntax
description of the basic type &v1& (customer enhancement &v2&).
However, the segment is missing in the <DS:GLOS.IDoc>IDoc</>. The
segment number logged in the status record identifies the item before
which the segment is missing.
This error may have been triggered by an unidentifiable segment before
the expected mandatory segment.

How to fix this error?

Please check the IDoc or the syntax description of the basic type &v1&
(customer enhancement &v2&).

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