By default, the AIP Backup & Restore functionality should be able to auto-create missing metadata fields during ingest/restore processes
(See 'createMetadataFields' option which defaults to 'true': https://wiki.duraspace.org/display/DSDOC/AIP+Backup+and+Restore#AIPBackupandRestore-AdditionalPackagerOptions)
Unfortunately, it looks like the fix to
DS-821 (AbstractMETSIngester creates an item before adding descriptive metadata) added to 1.7.1 caused this issue. So, this issue occurs in DSpace 1.7.1 and 1.7.2 (along with 1.8.0 Release Candidate #1).
I'm working on a fix for this issue, so that it will be resolved for DSpace 1.8.0. I'll also ensure that it obeys the needs of
DS-821 (so as to not accidentally reopen that bug).