Approval Workflow: Second Stage Not Triggered if Same User in Both Stages

We have a requirement to enable two-stage approval for supplier profile changes:

• Stage 1: Approval by a Sys Admin (role-based)
• Stage 2: Approval by an Approval Management Group

My user account has both the Sys Admin role and is a member of the Approval Management Group. When I made changes to a supplier profile, the approval process was triggered and routed to me for the first stage. After I approved it, the system did not trigger the second-stage approval; instead, both stages appeared as approved, even though I only approved the first stage. The timing of the approval is same in both stages.