I've found that Jetpack breaks the header when using anything other than 'featured image.'
The only workaround that I've come up with is to publish your content first (if you're using jetpack's publish to social media), then edit your post and update it (I don't have to change anything). This gets the content in the header correctly, then re-enable jetpack.
It's a bit of a hassle, but there is a duplicate code somewhere in the theme and jetpack.
A real fix would be preferred.