I could not figure out why the sidebar column of cover images was appearing only on the main page of this blog, but not the individual post pages.
I hadn’t meddled with the WordPress settings for a while – and I suspect in the interim, the theme I’d been using, now mysteriously called ‘Unnamed Lite’, had been revised. Some conflict between widgets was interfering with one of the two sidebars. Simplest solution, just install another two-sidebar theme. This one is called Coraline. I edited out the php to display the background image, and hardcoded a display of my preferred image… Now I can update the cover images roll.