Parent segment & has no children

What causes this issue?

Segment &v1& is flagged as a parent segment in the syntax description.
It has no children, that is segments that have entered segment &v1& as
parent segment, however.

System Response

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

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.