What I suspect is happening here, is because you are having people testing, I suspect they are flicking to the page, not seeing it, and closing the browser. Essentially just not giving it chance to load. As its native html that is being used there, its difficult to see what else it could really be. Possibly server response time, or even lazy loading if they are having to scroll to get the image and its not yet loaded up. As with others here, I am unable to see any issues to advise further.