When a RITM has multiple approval levels, there is no history of the previous approvals. ie. For example, after a manager (X) approves the RITM, approval request is sent to manager's manager (Y). When this approval record is generated, the previously generated approval record for manager (X) no longer exists.
This is an expected behavior when same "Approval - User" activity is called multiple times to generate the approval records, in which case, the previously generated approval record no longer exists.
Avoid calling the same "Approval - User" activity multiple times, instead call this activity ONLY ONCE providing list of all approvers at once OR use different "Approval - User" activities to generate those approval records, in both these cases the previously generated approval records will exist.