Cost line not updated
For example when copying an existing sale with an existing shipment cost line. On quotation the line may not be updated if the cost value is the same. But other properties like the taxes or the product could be different but they are not changed.
This behavior was inherited from previous version when the shipment cost line was computed with on_change in draft state for performance. But since rev 326087629a85 it is no more needed to have this optimization and could simply always create a new shipment cost line on quotation.