As you’ve seen, items info are stored in two locations: ‘items’ table
and with the biblio records. If you load data the way you’ve done it,
you have to ‘copy’ data from items table to biblio records. There is
script that can do it automatically for you:
The other option is to create directly items records during biblios
import. You have to put your item info into 952 tag for MARC21 records
(995 for UNIMARC).