Import Order Line, "Parameter name: Required field SalesOrder Id is missing" message display

SalesOrder Id has been contained in the xml file of order line，but when I imported the file for the first time with CDS Data Migrator,
it says 'Warning:DataCrmStoreWriter PersistUsingUpdateCreateRequests : Create Entity Issue salesorderdetail:a836c0a9-05d4-eb11-bacc-000d3aa1256e - Error:Value cannot be null.
Parameter name: Required field SalesOrder Id is missing'.
But I click the “Execute”button again, the data can be imported normally.(The content of the file has not been changed yet.)
What's the reason？Is there any problem with the operation?

In addition, the ‘description’ field cannot be updated by the field content in the xml file. The value of the ‘description’ field in the product entity is used to populate the field.