That screenshot helped a
bunch, Nick.
The issue is that the same variable names are being used for both the sidebox and page-content rendering, so the selected article's name was being overwritten by that left-side sidebox. I've opened this (
https://github.com/lat9/news_box_manager_v3/issues/23) issue on the plugin's GitHub repository to track to change required.
Note that the change is to /includes/templates/template_default/sideboxes/tpl_news_box_sidebox.php, so if you've made a template-override version you'll need to merge your changes with the subsequent update.