Aha! I see what you mean: clicking on Go advanced at the bottom of the space for a response, and then scrolling down, you see the same posts as in the previous page, but now the video is visible.
Great, with a little detour I can see the video's. Strange, however, that Firefox won't let me see them in the first place. I have AVG as virus protection, but in the past, video's would always show up. ( W10, 64 b)