UserAgent: Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.181 Safari/537.36

Example URL:
https://www.reptile-universum.de/index2.html

Steps to reproduce the problem:
1. Open the webpage https://www.reptile-universum.de/index2.html
2. Try to scroll the main frame
3. Problem: The background image moves while scrolling. It even moves in the opposite direction.

What is the expected behavior?
The background should stay fixed. This works with all other browsers. This webpage worked fine with older versions of Chrome.

What went wrong?
The style property "background-attachment: fixed" does not work as expected.

Does it occur on multiple sites: N/A

Is it a problem with a plugin? N/A 

Did this work before? Yes Not sure. I *think* this issue started in March or April this year

Does this work in other browsers? Yes

Chrome version: 66.0.3359.181  Channel: stable
OS Version: 6.1 (Windows 7, Windows Server 2008 R2)
Flash Version: