Segment & is used multiple times in IDoc types

What causes this issue?

Segment type &v1& is used multiple times in the IDoc type. A segment
type may only be used once in each IDoc type.

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?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.