You've worked out a rhythm - when the bowler hits the edge of the square you know you can start to walk forwards from the stumps without leaving early, and you get quite a distance up the pitch by the time the shot is executed - completely legally.
But then, the bowler stutters slightly in his run - either he hit the wrong spot, caught his foot on something or whatever, but all of a sudden you've left your crease fractionally early, even though every other ball you've been fine and are intending to completely adhere to the laws of the game.
Do you deserve to be run out in that instance, assuming the bowler picks up on it and gets the ball onto the stumps (minor detail, I know
).