User Agent: Mozilla/5.0 (Windows NT 10.0; rv:64.0) Gecko/20100101 Firefox/64.0 Build ID: 20180919003800 [Affected versions]: Nightly 64.0a1 (2018-09-19) (64-bit), Nightly 64.0a1 (2018-09-19) (32-bit) [Affected platforms]: Windows 10 x86/x64 [Steps to reproduce]: 1. Launch Firefox with a new profile 2. Type about:config 3. Set gfx.webrender.all.qualified = true 4. Navigate to https://belen-albeza.github.io/scroll-demos/parallax.html 5. Scroll down the page with mouse wheel/scroll bar 6. Scroll top the page [Expected result]: The parallax effect should be displayed without any interruption. [Actual result]: The content of the site is incorrectly loaded while scrolling .