Featured image also appearing as header

Hey folks. I’ve set a featured image for an article which works fine on the homescreen, however when I go to the article page it also appears as a header behind the image I already have there (which is in a custom text widget, not set as a header).

This is only happening on this one post though, other posts I’ve set featured images don’t also show it in the header. Here’s what the problem page looks like:

Any idea how I stop this from happening?

Many thanks,
Cameron.