I have discovered a bug with this widget and did some testing to discover when the bug appears. My set up was 4 icons that represent photos, video, interactive, event. Those link to different collections. When I was all my content was inserted according to the tutorial I would get random white gaps in the layouts in both preview and online but I could hover and click on the emptyness and see a light room image and sometimes no image at all in lightroom. I started over to see at what point the widget fails and it appears to give issues when I start the second collection.