How to change the serialised item on subsequent snapshots
Problem
New sales order with serialised stock on back order (Manual back order mode). Process the order
Create a new snapshot and deliver the serialised stock and save
Close the sales order form and reload it and you can't change the serial numbers for the items selected
Solution
You need to select Reduce Deliveries from the Utilities tab and save. That recreates the back orders and puts the stock back.
Process the order
Create a new snapshot and deliver the correct serial numbers for each item and save