How to stop featured image from replacing header in Lovecraft Theme

I’ve just switched my entire website over to the Lovecraft Theme. I’ve got most problems worked out, but the one thing I can’t figure out is this: The featured post images are replacing my website’s header.

I want the featured images to be displayed at the top of the post and as thumbnails elsewhere. Not to replace the header. I have several other WordPress sites and I’ve never had this problem.

This problem has nothing to do with the size of the images, either. I’ve already looked into that.

Is there a way to edit my header.php or something else to fix this? If not, is there a plugin to correct this?

I’d really appreciate a fast response. Thank you!