I'm having an issue when using the trackpad on my 2014 15" MBP. My Guest OS is Windows 8.1, Parallels Desktop version 10. The problem occurs in Window, Coherence, and Fullscreen modes. When scrolling with the two-finger gesture on the trackpad, Windows responds as though the tracking is very very slow. It takes about half the vertical distance of the trackpad to get Windows to scroll one "notch" in a document. Increasing the scrolling speed in Windows doesn't help, because it doesn't receive a vertical scroll event until I have moved my fingers a large distance on the trackpad. I have tried all the mouse settings I can find, but nothing seems to affect trackpad scroll-tracking speed. The wheel on an external mouse works fine. It's just the trackpad.
Update - I had missed one setting in my earlier experiments- "Smooth Scrolling". Disabling this feature resolved my issue.
