Assess the problem of requisitions raised without filling the field Nature of Transaction on requisi

Some Requisition is being getting created without "Transaction Nature" mandatory field requisition page in EBS 11i.

Recently we have been provided with some of the list of requisition for which "Transaction Nature" field on Requisition Screen i.e 'Transaction_reason_code' of PO_REQUISITION_LINES_ALL table value is NULL. This filed is mandatory in the requisition page of our project and has list of values to choose with it.
But we are really not sure how those requsition got created.

We are trying to simulate this issue in our DEV instance but we could really not able to craete requisitions without this field 'Transaction_reason_code' .