The following happens:
1. SO no 1 with different Partner Location and Invoice Location.
2. Then do a manual Shipment(Customer) against SO no 1.
The Partner Location on the shipment does not default to the Partner Location as per SO no 1.
As far as I can see the callout org.compiere.model.CalloutInOut.order does not set this value on the Shipment(Customer) window.