I setup a test site and the lightbox feature is not working on my mac running OS X 10.9.5 on firefox 42.0 .
The lightbox feature is working on other browsers (Safari and Chrome) but when you click on either of the videos on the page in Firefox no lightbox shows up and it makes the page scroll to the top.
The strange part is that I checked out some of your example sites and this one is working fine in my firefox so I have a feeling it could just be something that might need to be clicked,checked etc. Site that works: http://dryphonecase.webflow.io/#uses
Thanks in advance!!