Reported by dfaber:

The youTube-embed-block on post-pages is creating a large empty space at the bottom right now, due to the padding-bottom on the inner div. I know why this padding is there (aspect ratio), but it is already defined in the "inner-inner block", so you now have it twice. Have a look at https://www.greenpeace.org/international/story/46082/climate-activists-on-system-change/ to see what I mean.

Extra info from stduerre: Vimeo embeds were also affected for us, so maybe it makes sense to check those. They are positioned the same way.