Entry "&1" will be deleted (see long text)

What causes this issue?

There is data in the secure storage that should be deleted for security
reasons after a change in the identity of the system.

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

Since there is no suitable time at which the application code can be
executed after an identity change, the administration functions of the
secure storage are used instead.
If this function detects that one of these entries exists, but cannot
currently be read (this is normally caused by a change of identity), the
entry is deleted.

System Response

The situation described above applies for the following entries:
/HMAC_INDEP/RFC_INTERNAL_TICKET_4_TRUSTED_SYSTEM
The RFC identity of the system for internal RFCs. This entry is deleted
if the system ID or the installation number has been changed.
This entry is automatically recreated by the system, as soon as an
internal RFC takes place.
/HMAC_INDEP/RFC_EXTERNAL_TICKET_4_TRUSTED_SYSTEM
The RFC identity of the system for external trust-based RFCs.
This entry is deleted if the system ID has been changed. Use transaction
SMT1 to recreate the trust relationships to external systems.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.