Hi Sam,
Full Load :- This always comes from Set Up Table and it picks up from the Tables..as it is one time activity.
Delta Load :- This always comes from Change Logs ..as it is Delta.
When a Quantity in Sale Order is changed it gets triggered as Delta Changes..so not every field in Sale Order is Delta Enabled...So here may be Ship to Country is not Delta Enabled...And Can you check if you can add Ship to Country to 0CUSTOMER master and then read it from as an Attribute.
Rgds
SVU