Open Radar

 
Summary:
This problem exists since I have my MacBookPro Retina 15" (late 2013). It doesn't happen often - maybe about once every two weeks - but when it happens it is very stubborn.
I first noticed in Tweetbot.app, that all scroll gestures begin to be blocked when I did a 2-finger-swipe gesture on the trackpad to left or right (to change views). Then it is like every two-finger gesture (scroll or swipe) doesn't work anymore (neither using the trackpad, nor using the mouse). After restarting the app scrolling worked as before but just until I did a left-right swipe again. This persisted until I found a solution on discussions.apple.com which said I had to reset NVRAM and PRAM. I tried it and it worked. Afterwards the problem was gone for some days or a week.
Unfortunately in the last time I often see the problem with Safari too (basically when I try to go a page back or forth). So I guess tis problem is system related and not just a problem of the App. (I also saw it in Chrome.app)

Steps to Reproduce:
1. Open a web page and click on a link so that it forwards you to another page
2. Swipe to the right with two fingers on your trackpad
3. Try scrolling

Expected Results:
Swipe to the right (step 2) should bring you back to last visited site and you should always be able to scroll on the webpage.

Actual Results:
No two-finger scroll gesture is working anymore (i.e. blocked UI). One finger gestures (e.g. moving the mouse pointer) works. Clicks react (clicking on the back-button of Safari works and brings you back to the previous page).

Version:
OS X 10.9, 10.10

Notes:
Resetting NVRAM and PRAM brings a temporary solution.