I am using SJ News ii and have a long-standing niggle.
When the template is at some widths on a desktop the background becomes transparent and looks broken. It does it on my site and also on the SmartAddons demo server.
Full width - fine:
https://ibb.co/fkMDh7S
But on a narrower browser - background transparent:
https://ibb.co/6b4fdWV
It should be a white background all the time. It's fine again at very narrow.
Tested on the demo server: demo.smartaddons.com/templates/joomla3/sj-news-ii/#

I can't work it out. Any ideas anyone?

Please you go here www.smartaddons.com/support/tickets submit a ticket.