UPDATE: Managed to resolve – updating the Unyson extensions seems to have fixed this.
Many thanks, that works great now – appreciate it!
P.S. When following the link, the photo opens directly in a tab (rather than in a lightbox as expected):
https://www.dropbox.com/s/x9oj7lv3klwxec8/Screenshot%202017-06-03%2019.51.05.png?dl=0
You can also replicate this on: