Windows 10, GeForce 1060
Broken: (2.79RC2 (but have observed this behavious at least a few versions back))
Short description of error
The most recent actions in Undo History are hidden/off screen.
Exact steps for others to reproduce the error
I can't attach a .blend file as they don't keep Undo History to my knowledge. However start blender and perform random actions until the Undo History fills the whole screen. Eventually the row with the most recent actions will be outside the screen area. You can still select them but only blindly. I think actions with long names increase the likelihood of this happening but I am not sure.