I made a page header using a block element for pages & posts (and excluding the front page). It’s using dynamic background images, using the features images for a post or page.
Here it is working fine on a page: https://www.quackatoa.com/about/
The problem is that it is only working on some posts. Here is the blog page, where you can see that each post has a featured image selected: https://www.quackatoa.com/blog/
You’ll see that the first two posts (#21 & #20) have the header working fine when you go their links. But the 3rd one (https://www.quackatoa.com/wisdom-from-comics/) has a missing header image.
Is it due to the size of the image? For the example link above, the size of the missing featured image is 1334 by 750 pixels.