When you are trying to update records using CSV imports, then you might end up getting error “Ambiguity error on logical key multi-match” when one or more line is having same item.

You will need to assign Line Numbers to each of the records you are importing and then map them to the Order Line No in NetSuite. This order line number is a special mapping which is not seen on record but you will get this field in line category to map during CSV field mapping.

For more details visit Line Item Updates on Transactions Imports