When Buffy and Faith are at the dock and the pile of boxes drop over Buffy, vampires attack Faith. Between shots, Buffy is sitting and watching the fight (when the camera is on Faith) and lying down on her back (when the camera is on Buffy).
When Buffy knocks at the French doors to Willow's bedroom, Willow opens the half to Buffy's right (Willow's left). They talk, then as Buffy starts to enter we see her (from behind) pull open the door on her left (the half Willow did not open) using her left hand. But when the view cuts to the reverse angle, that door is suddenly closed again and Buffy is facing the opposite way, pulling *closed* the door to her *right* (the one Willow opened originally) using her *right* hand.