If the resolution of each monotor in a dual screen is setup such that a "void" space exists in the overall "screen" then the screen edge features such as hot corners and dragging windows to a different desktop no longer work.

Reproducible: Always

Steps to Reproduce:
1. Set up dual monitor with two different resolutions (eg: 1920x1080+0+0, 1680x1050+1920+0) so that there is a void space.
2. Assign a hot corner to the corner in the void space (lower right in the above example) and try to activate it.
3. Try to drag a windows down to a virtual desktop below on the second screen.
Actual Results:  
The mouse never reaches the active edge due to mouse clipping preventing it from entering the void space.

Expected Results:  
The active screen edge is moved up 30 pixels on the second screen allowing the edge to be activated, windows can move to lower desktops and the hot corner would work

This became a problem a few months back when one of the systems (Xorg or kwin, I'm not sure) implemented mouse clipping to prevent moving things like windows into the void making them unreachable.
For fun and profit have the right screen in portrait orientation with the left one shifted down to be centred.