Comment 31 for bug 1264795

I've been doing some research after experiencing this issue, and stumbled across this. It may be nothing but for me this only seems to happen when my MacBook Pro is connected to the mains. When unplugged it goes away, and also when keeping a finger touching the chassis whilst using the touchpad, it also hasn't happened yet.

I didn't notice this under OSX so maybe there's some extra checks going on behind the scenes there for contact patch size or reduced touchpad sensitivity.

Steps whilst plugged in,
1, use laptop for a while
2, two fingers together on touchpad (not touching anything else), swipe slowly and gently upwards to scroll the page
3, alt tab switcher opens, switches to next window, closes, instead of scrolling upwards

Laptop unplugged or with a 3rd finger touching the metal body? Nothing unexpected happens.