(If you need to reproduce)
I have a 4000pix wide header in my Themes>essential>header>Header background image
It's set to a fixed background, no tiled.
I have Set page width Themes>essential>general set to Variable.
I want to have the header fixed when you zoom in and out.
When you zoom into the page, spaces appear either side of the header like it's not long enough.
This is even if you zoom out 90% in Chrome.
I have tried different image lengths from 2000 to 6000 pixels and nothing makes a difference.
I can't tile the image the image looks warped to the users when you zoom in and out.
How do you stretch the header so it stretches the page?
I'm happy to PM a pic if needed.