When a menu extends too far (and you cannot right click to open the menu any higher on the screen), it often reaches the bottom edge of the screen, which causes map-scroll to occor when you go to the bottom of the menu to click a selection or the more-arrow.
Easy way to reproduce.
Enable full-screen mode.
Start a new game.(paused option on)
Right click on your stack of civilians.
If your resolution setting doesn't cause the right-click menu to reach the bottom, convert all the civilians into soldiers, the extra options for soldiers spread the menu even further.
Once it reaches the bottom, observe the downward map scroll when you try to click the More -> option.