CSS failing to load causes strange look of post

Many thanks for the great theme.

I’m experiencing an intermittent problem when displaying selected posts. The posts on this website mostly have a similar style. Below the top bar menu I’m expecting to see: (1)title of the post (2)categories of the post (3)an image I put in the post as the first item. This usually works fine. But on some occasions, above the title, I’m seeing half of the same image that appears below the categories. It is split vertically but same width. It’s as if I had set the feature image (but which is not set on the post).

If I refresh the page, the problem goes away. Once fixed, I’m unable to duplicate the problem on demand. I did manage to fire up the Web Developer => Style Editor on Firefox on the faulty version. Firefox notified me that the CSS could not be loaded. Below that, the code suggested something about an image of 1170 x 250 in size. The width is fine but the height isn’t what I specified. My img has a height of 400. So it looks like something is grabbing my img and treating it as a feature image. Does this make sense?

The page I need help with: [log in to see the link]