Archived cases are being archived, but not being indexed to custom index
I've set up case archival on different environments by creating an Archival Policy of 1 day for a certain case (instance of Data-Retention-Policy). I've configured the job schedulers pyPegaArchiver, pyIndexer and pyPegaPurger to run with an interval of respectively 3 minutes, 3 minutes and 20 minutes.
I noticed that items are building up in the metadata-table (Data-ArchivalMetadata) on pyArchiveStatus = Archived but they don't move forward to Pending-Purge. I see the pyPegaIndexer running successfully on Log-IndexerResults but I don't see any items being picked up for indexing. Also, I don't see a custom search index being created on the Search landing page.
I'm facing this issue specifically on the Staging environment, but also noticed it took a while on other environments before items are being indexed/purges (but not so long).
The activity pzPerformIndexing calls pega.performIndexing() and from there it's less visible what happens in the Pega engine.
Any ideas why the indexing doesn't start after cases are being archived?