Hi Slartifartfast,
I had the same problem. What I did?
Format Standard
uploaded picture to media
From media set as featured image
insert to post.
add content (optional)
Delete image in post and publish.
When I did that repeatedly, I had only one image. I noticed If I set format gallery and delete, the image appears as featured image but not in the blog/post. But when I set format as standard and delete, the image will appear in the post and as featured image.
