Ok, you’re all fixed up. There’s new plugin installed on the site called Code Snippets. This has a code snippet which will run if both Stack and Connections are active. When run, it will enqueue the theme’s older version of the picturefill library. Connections will merrily go on its way loading the current’ish version it requires.
If you have a moment, I would truly appreciate a review as they really do make a difference. Many thanks in advance!