There are documents that are automatically generated via the repair process of customer owned goods received for repair on customer deviation documents (CDV's).

When a repair is started, a customer order (COA) is created and flagged with 'CUSOWNEDRETURN'. 

The customer order (COA) gets one item that contains the product that has been received to be repaired. 

This item on the customer order (COA) is automatically flagged as picked in this process, based on the logic that when the repair is started, the product is physically on hand and being worked on.

To replace the defective parts in this product, the user works on the life-cycle management document (LCM), in the part list tab. Parts can be exchanged, and there is access to the picking application to print out a picking list and confirm the parts that must be found in the warehouse and inserted into the product being repaired.

When the repair is completed, the user transfers the customer order (COA) to the shipping advice (CSA). 

At this point, all the items have already been picked, according to the description above. 

That is why the picking list on the shipping advice (CSA) is "empty". (print of picking list on the shipping advice (CSA) contains only those items that have not been picked).