Snapshot feature not working with 'treat as lightbox' in Applied Actions

I’m trying to use the Snapshot feature to export screens as images in various different states. I need to show a hidden dynamic panel as a modal window - so in Applied Actions I have used Show/Hide to Show the dynamic panel and set it to ‘treat as lightbox’. The dynamic panel does show, but not as a lightbox. A colleague had the same issue.

Is this a bug or am I doing something wrong? Thanks!