SAP Note 3349110 – How to report efficiently a problem to the SAP Product Support in the area of BC-SEC-USR*?

Start from the very beginning.

1. In which system is the example?
2. Which client of the system?
3. What transaction is used?
4. What data will have to be entered where?
5. What buttons have to be clicked on?

Let the engineer know exactly what steps need to be followed to re-create the error.

KBA: 1773689 – How to add S-User ID logon credentials securely to an incident

SAP Note 9 – Error cannot be reproduced: No solution

Also see SAP note 2522341 – Change priority of an case sent to an SAP Partner