Front Page post mirroring revisions to other pages, constantly updating itself

The issue was my theme; a recent update to it (Hestia Free v1.1.51) caused Page Builder by SiteOrigins to break page updates by copying the updated page content to whatever page was set to the Static Front Page. That version of Hestia also generated numerous page updates to the static front page, often many per minute.

I have rolled back to Hestia Free v1.1.50 with WP Rollback and the problem has vanished. I will contact the theme creator.