In the past, we've ran into questions as to why a trigger did not apply to a particular order after it was set up. For example, if you would like an item to be added to every new order that is within a specific LOB, your smart filter selection criteria would need to be for LOB 123 and Status On Order. Your Trigger must be set to "Insert" and the action should be "Add Item" with the proper item information added to the form when completing.
This will ensure that the trigger is ONLY applying the smart filter to all new orders with LOB 123. If your smart filter status is not set to On Order, the trigger will search for every order within that LOB, and apply the trigger only to the new orders and create error messages for all existing orders.
A good way to keep track of whether triggers are applying is to set up Notifications on the dashboard. This will display all errors running triggers and make it easily accessible to view.