Group Level approval process

In Workfront, we currently use a Group-Level Global Approval Process. Recently, due to organizational changes, two users were reassigned to a different manager. We updated the Multi-Eye Reviewer in the task approval process following an employee's departure from the organization. However, when running approval reports, completed projects no longer display approvals performed by the previous manager or former Multi-Eye Reviewer. How do you manage approval process changes in your environment to preserve historical approval records? What are the recommended best practices for updating approval workflows while ensuring approval history remains intact on completed projects?