so I got this extremely strange scrolling bug on my Windows 8.1 Lenovo Yoga 2 Pro. When in an metro app or the start screen scrolling works as expected, but when I'm on the desktop in any windows whatsoever (Chrome, File Explorer, name it). Scrolling doesn't work properly anymore. There's this strange square popping up for a millisecond which looks like when you press and hold on the touch display before the secondary click popup pops up.
I tried reinstalling the drivers, but that didn't work.
I disabled two-finger scrolling in the trackpad settings and then the square thingy doesn't popup anymore, which indicates that this is directly connected to the scrolling itself and not some other conflicting gesture.
UPDATE: Turns out the problem goes away once I connect an external display but reappears after I disconnect the display.