Performance rating update after calibration meeting

In our Performance Management, the process is like below:

First employee evaluates himself/herself, then manager evaluates the employee and when the manager submits the evaluation, the First Approval step is being automatically fulfilled and the performance document is being in Completed status, so no one can do any change to the performance document. Then business does calibration meetings with managers and after calibration meetings there can be changes in calculated ratings. For example, before manager has evaluated the employee as ‘Exceed Expectations’, then after calibration meeting they determine that the employee should be re-evaluated by manager and rating should be done as, for example, ‘Meet expectations’ and also calculated