Default Source org is incorrect in IR

For a Internal requisition  an Item has source information mentioned in the Item attributes tab of general planning and also same source information in mentioned in preferences and  in preference destination information is mentioned. when we try to create new IR destination and source information is retrieved in IR as mentioned in preference. once item entered in requisition, Source organization is changing to other which are not defined either in item attributes or requisition preferences. Do we have any other setups to default source organization in requisition form.

Thanks