This was some how being caused by a conflict with WP Lightbox 2 which is an abandoned plugin. Once I stripped that from the site, the error went away and all is well! The only other (unrelated) issue I had was my repeater template had self closing icon tags like:
<i class="tt-icon" />
When rendered, they were not being closed correctly and caused formatting issues.Easy fix but didn’t seem to be an issues in the last version.
<i class="tt-icon"></i>
Thanks for the support and for the great plugin!