BPM Worklist Notification to Initiator when Approval is escalated is not arriving

Summary:

Hi everybody, 

this scenario happens when I test the action "Escalate" in the Approval Workflow of an employee: 

The Line Manager initiates the process.The approval chain consists of 3 approvers in this sequence: 2nd Line Manager, HR Partner, Controlling. 

When the HR Partner escalates the approval to his boss, the boss gets the Approval step. We expect that when the Boss of the HR Partner rejects, an information will be send out to all previous approvers/assignes.

The line manager and 2nd Line Manager get a notification about the rejection and can see in the process history that it was rejected after escalation. However, the HR Partner doesnt get any notification.