Hi Lloyd,
It’s difficult to say without logging into your site. But based on your screenshot it seems you have accidentally added a header within a header.
In the top left of the editor, just to the right of the blue “+” button, you will notice an icon with 3 vertical lines. This icon is for your “List View”. I would recommend toggling the list view option, and then looking within the list view on the left to see if you have any duplicate blocks nested in other blocks.
The list view provides a nice hierarchy for viewing and editing blocks, and it’s especially helpful in cases like this.
Let us know if this works.
Thanks!