How to retain cases for terminated employees in Case Management

We are experiencing an issue where

• terminated employees are not in the primary contact LOV even though the profile option ORA_HELPDESK_CONTACT_TERMINATED_EMPLOYEES is set to all
• when a terminated employee is the primary contact of a case, the case number is "n/a" and clicking it results in an error

We need these cases to be active as some of them are in progress