Ok, I ran made some test post and this only seems to be happening when I use a “featured image”.
This seems to be a plugin conflict as I am using (or trying to use) Auto Excerpt everywhere plugin to show excerpts on blog page. This works fine if I set a featured image. However, if I set a featured image then my header doesn’t work right.
If I disable the auto excerpt plugin then I don’t have the problem.
How can I show excerpts on blog post page with image thumbnail and not mess up my header?