UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.62 Safari/537.36

Example URL:
http://klixtheme.com/demo/all/colorful/tables/

Steps to reproduce the problem:
1. Open http://klixtheme.com/demo/all/colorful/tables/
2. Scroll down

What is the expected behavior?
Background Image (http://klixtheme.com/demo/all/colorful/wp-content/themes/klix/images/blog-default-bg.jpg) should stay in background.

What went wrong?
Background image is moving down when scrolling the page down and moving content up. 

Does it occur on multiple sites: N/A

Is it a problem with a plugin? N/A 

Did this work before? Yes 66

Does this work in other browsers? Yes

Chrome version: 67.0.3396.62  Channel: stable
OS Version: 10.0
Flash Version: 

Background Image is loaded after flash images can't be loaded. 

		<div id="background">
			<div id="swf-bg">
				<!-- the image in the style attribute is the backup image for non-flash -->
				<!-- delay the backup BG showing so it doesn't flicker on before other stuff is loaded -->
				<style type="text/css">#html-bg{visibility:hidden;}</style>
				<div id="html-bg"></div>
				<style type="text/css">
				#html-bg {
					background-image: url('http://klixtheme.com/demo/all/colorful/wp-content/themes/klix/images/blog-default-bg.jpg');
					filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(src='http://klixtheme.com/demo/all/colorful/wp-content/themes/klix/images/blog-default-bg.jpg', sizingMethod='scale');
					-ms-filter: 'progid:DXImageTransform.Microsoft.AlphaImageLoader(src="http://klixtheme.com/demo/all/colorful/wp-content/themes/klix/images/blog-default-bg.jpg", sizingMethod="scale")';
				}
				</style>
			</div>
		</div>