Requisition created for an operating unit which user has no access to

I have a very usually scenario that I am not able to resolve.

This scenario applies only to a few users and it is difficult to replicate.

A user has access to create requisitions for operating  unit ‘A’ and he has only assess to A-iProcurement Responsibility .

When his session expires, and he needs to login back to Oracle and try to create a requisition, somehow the requisition is created for a different operating unit ‘B’, and he doesn’t have access/ responsibility to create requisitions for a different operating unit.

I don’t know how that is happening and how to resolve this issue .