Change Authoriser does not work properly.

All,

List of approvers shown before approval submission in Oracle R12 IProc doesnt reflect the overriding requested. List shows the overriding approver as first approver in chain and requestor's manager as final approver eventhough the overriding approver has sufficient approval limit to approve the requisition.  

For eg. Let say X,Y,Z  are individuals in an organisation. X's manager is Y. But Z asks X  to create a requisition and submit to him for approval. When this requisition is getting submitted, list of approvers in IPROCUREMENT is shown as

Requsition document -> Z->Y. 

This happens sporadically. Any help?

Thanks,