user can't create sale order : (Document type: Add the New fileds into the Sale Order, Operation: create)
Check the Salesperson tagged to that sales order.. if it shows any other user(which is not logged in user).. then it won't allow the record to save.. Select the logged in user in Salesperson field, then the record will get saved without errors.
other users will be tagged as salesperson if customer is having another salesperson other than logged in user... so you can remove salesperson from that particular customer..
so: pastikan user yg membuat SO tidak mengisi salesperson dengan nama orang lain