[Koha] Editing Biblio deletes the attached items?

Version 2.2.0 a) We edited a biblio to make a change to the ISBN # and it deleted all the attached items? b) In previous version, data entry prevented duplicate items numbers, how to activate this feature for version 2.2.0 ? Background: We run a text book library for a college, and have as much as 150+ items per biblio record. Editing biblio and losing all 150 items currently on loan is not a pleasant thought. :(