If you have multiple monitors, and just have full screen on one of them, the edge scroll mechanism can misbehave. The problem is that we do not handle the cursor leaving the window properly. Known issues:
a) On mac the pointer is tracked constantly, not just inside the window
b) Leave events aren't properly handled, meaning we get varying amount of scrolling on the edge the cursor left.
We cannot simply ignore mouse events outside the window as the user probably wants dragging to trigger edge scroll, even when leaving the window.