Tested with mod-oai-pmh-3.2.5: when only holdings or items are added or modified, harvesting does not pick the records unless the instance record is modified as well.
Steps to Reproduce:
- In inventory app, choose an instance with underlying MARC record (you can use the Source filter set to MARC)
- Update existing holdings and item record (modify permanent location and add electronic access information) or add a new one.
- Start harvesting with https://<oai-pmh-url>/oai/<apikey>?verb=ListRecords&metadataPrefix=marc21_withholdings&from=<date>
Response contains instance with updated holdings/items data
The record is not returned until the instance record is updated as well (you can update the underlying MARC record by using Edit in quickMARC option in Actions menu)
I can recreate the issue on rancher and concorde5c environments.