Affected versions:
88.0b2
89.0a1(2020-02-24)

[Affected platforms]:
Platforms: Windows 7/8, Ubuntu 20.04

Graphics Cards:
Nvidia Geforce 730
Intel 530, 4600

[Preconditions]:
Reach about:config and set both gfx.webrender.enabled, gfx.webrender.software - true

[Steps to reproduce]:

1. Launch the Firefox browser.
2. Reach amazon.com and perform any search, ex: https://www.amazon.com/s?k=zelda&ref=nb_sb_noss
3. Start scrolling slowly using the middle mouse button or scrollbar

Expected Result:
Scrolling should be smooth.

Actual Results:
Scrolling on Amazon is jerky with Webrender Software enabled

Notes:
Not reproducible with Webrender Software disabled nor Webrender disabled.
Couldn't get a proper screen-recording (it hinders the overall performance) and my phone doesn't record the frame where the scroll is jerky.

Webrender Software profiler (repro): https://share.firefox.dev/2PmVj6O
Webrender simple profiler (not repro): https://share.firefox.dev/3vTu2d7