In the final scene when Darth Vader is pursuing Luke on the Death Star, watch the sequence of events very closely.
Vader locks on,
Vader fires,
Han Solo Comes in and blasts Vader away!
Wait a minute! If Vader had already fired, while being locked on, Luke's X-Wing would have been seriously damaged if not destroyed. Did Vader miss? Not likely, and he hasn't missed with any of the other How can the scene continue like nothing happened?