I think it's because your looped demos are autoplaying videos. Modern browsers can control media playback, and presumably these autoplaying videos are hijacking the currently played media for some people?

As an aside, I was actually looking for a comment about the opposite issue: I have a browser which blocks autoplaying videos, it took me a while to realise that what I thought were static images, were in fact videos without playback controls (and a little bit longer to work out how to re-enable playback controls!).

Either way, once I got them playing, it looked like a slick experience, congrats on the launch!