Mouse Animation Incomplete, Timing "Rest of Slide"

A mouse object is somewhat different to other types of slide objects.  You would NOT normally want to set it to Rest of Slide because that would mean the mouse movement starts when the object first enters the timeline and does not finish until the very end of the slide timeline.

If you want your mouse movements to appear more natural, the better way (in my experience) is to keep them relatively short and stop just a few tenths of a second BEFORE the end of the slide timeline.  That will mean the mouse movement should more or less match how many seconds it took for the user to move the mouse to the new location and click the mouse button.  I stop the mouse movement a bit before the end of the slide because with most software there is a slight delay after you click something before the screen redraws or moves to the next page / website etc.