Flicker when scrolling

[jskn]

First out: Great looking theme! Thanks for making it open source.

Describe the bug
Some flicker/glitch in white at the bottom and top of the page when scrolling.

To Reproduce
Choose a longer article. Scroll in "skim reading" pace, now and then you should see a white flicker. Both scrolling down and up again.

Expected behavior
No flicker when scrolling. It seems to work in Firefox.

Screenshots
Example in this video https://share.cleanshot.com/v4mhuY

Desktop (please complete the following information):

• OS: Mac OS
• Browser: Chrome and Brave
• Version: Latest versions.

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.