NetSuite Connector Carrier Handling
NetSuite Connector gets the carrier from the shipment method name on the fulfillment. For example, if the shipping method is called FedEx 2 Day, NetSuite Connector derives the carrier value as FedEx. However, if the shipment method is generic, NetSuite Connector uses it as the carrier since the carrier ca cannot derive the carrier, usually NetSuite Connector sends the shipment method as the carrier. If you have multiple generic shipment methods or uncommon carriers, you'll need to create mappings for the Carrier field or use a custom field.
When you sync orders to a 3PL for fulfillment, you can map shipment methods coming from 3PL to a different shipment method in NetSuite. However, make sure the shipment method mapped in NetSuite uses the same carrier as the one used with the shipment methods in the 3PL.