Sender fields must be unique in their first 8 characters: &1

What causes this issue?

Generation of a preliminary program is terminated because the name of
the sender field is not unique in its first 8 characters. This name is
to be displayed as a parameter. However, parameters in reports may not
be longer than 8 characters.

System Response

The name is cut short.

How to fix this error?

Rename the sender field so that it is unique in its first 8 characters.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.