No logs or audit trail for mysterious reassignment of category options

On a very busy 2.31.8 server we are experiencing a strange phenomenon where ~100k Category Options are unassigned from their Category Option. We can’t (yet) explain what is causing this and we know there are not any custom scripts at play (internal or external). No NGINX logs that describe these changes. No dhis.log entries that describe these changes. No API lastUpdated or lastUpdatedBy values that describe these changes.

Has anyone ever encountered something like this?
Jira Ticket: https://jira.dhis2.org/browse/DHIS2-8870

Related Jira:
https://jira.dhis2.org/browse/DHIS2-8181

Related CoP:

Happened again this morning, and today it is not allowing to re-assign the category options back to the category.