Changing approvers on an issue with multiple approval steps appears to change approval history in the Customer Portal for earlier approvals

Issue Summary

This is reproducible on Data Center: no

We have been progressively rolling out a new feature that allows admins to exclude reporters or assignees from approving requests. This changed the way we calculate lists of valid approvers, and introduced a bug in how we display of approval history in the Customer Portal. This bug only affects requests that go through more than one approval status and use the same field for approvers. In later approval steps, removing an approver from the approvers field will cause that approver's decisions to disappear from history on earlier approvals. This is only affecting the Customer Portal; the Agent View is unaffected and will show the correct history.

Steps to Reproduce

1. Create a Workflow or Modify the Approvals Workflow to Include a 2nd Approval Step.
2. Ensure the Same Approvers Field in used for Approve Step in both the Approval Status ( Select All Status can Transition to Speed up the process )
3. Publish the Workflow and then create a test ticket from the Portal ; Add a Approver ( Example : ABC ) 
4. Login as ABC and Approve - > Transition to 2nd Workflow Steps
5. Manually ; Clear Approver Field and Replace it with another User ( Example XYC ) 
6. Login as XYC and Approve. 
7. Once approve login in customer portal and you will see that XYC is also seen in Approval Step 1.

Expected Results

The request should display all the valid decisions recorded for the previous approval.

Actual Results

The decisions made by earlier approvers will disappear after they are removed from the approvers field

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available.