Mouse cursor jumps to top of screen at random times At random times, my mouse cursor jumps to the top of the screen in the middle of the status bar for no reason at all. This used to happen on my previous install of El Capitan but stopped when I did a clean reinstall. Now the exact problem is happening again.

This seems to happen mostly when I am running in clamshell mode, connected to an external display while using my Magic Mouse. But this doesn't seem to be the issue since it resolved itself when I reinstalled.

I installed the Microsoft Office 2016 suite, Live Interior 3D Standard, Firefox, Skitch, and LaTeX recently. Could these be causing these issues? Is there any way to see "recently installed daemons" of some sort? New LaunchAgents, for example?
In my opinion, you should clean your Magic Mouse and your desk (dust, hair, ...).
I don't think it is software-related.