Oracle session closes when cancelling multiple purchase order shipments.

We have intermittent instances where we lose our Oracle session after cancelling the the 3rd or 4th purchase order shipment. This does not always occur and is difficult to reproduce on demand. When we previously opened an SR, we were told not to open the purchase order and to drill down to the shipments. We have been doing that process and still occasionally experience session freezes. I have attached a document of the process we use. What we want is the ability to cancel as many different purchase order shipments as we would like without losing our Oracle session.