Hi Anthony
Thanks for the report.
I suspect it’s the addBack function. The ‘addBack’ function has been in jQuery since v1.8, so I think your version of jQuery must be 1.7 or below, which is odd because the default version of jQuery shipped with WordPress is v1.11.
I think your theme must be using an old version of jQuery. Please try installing the jQuery Updater plugin, if that doesn’t work please send me a link to your site and I’ll take a look.
Regards,
Tom.
Hi Tom
Thank you very much – that was exactly it as I was running jQuery 1.7.1.
I had deregistered jQuery to use that version from a while back and didn’t even noticed it was out of date, great spot.