Revealing mistake: When we see Spike and Andrew on Spike's motorcycle talking about Onion Blossoms, a filming light is reflected in Andrew's helmet.
Lies My Parents Told Me - S7-E17
Continuity mistake: After Spike finishes reading his poem to his mother, the piece of paper that it's written on disappears from his hands between shots. We never hear or see him put it in his pocket and he doesn't move to put it down on the table beside him.
Storyteller - S7-E16
Revealing mistake: When Buffy, Spike, Andrew and Robin go to the high school and find it decimated, Buffy is thrown to the ground and attacked with a hockey stick. On the second swing, a sound effect is heard and Buffy falls over. But the hockey stick never makes contact with her.
Get It Done - S7-E15
Audio problem: When The First uses Chloe to mimic Buffy, Chloe's lips don't quite match her words.
Continuity mistake: In the final scene with Buffy and Willow at the end of the episode, the position of Buffy's right bra strap keeps changing throughout the entire scene.
Visible crew/equipment: After Gnarl poisons Dawn and traps Willow inside his cave, the shadow of a camera is visible on some bushes on the left side of the screen as we see Xander and Buffy carrying Dawn home.
Seeing Red - S6-E19
Continuity mistake: Shortly after Spike tries to rape Buffy, he returns to his crypt and drinks a glass of vodka. Clem then arrives to watch television with him. During Spike and Clem's conversation, the position of the bottle of vodka constantly changes between shots.
Visible crew/equipment: When the Scoobies are attempting to leave Buffy's house by using magic, we see a close up shot of the house's front door knob. None of the Scoobies are reflected in the door knob even though they're standing right in front of it. There is also a fairly large black object reflected in it. A film crew perhaps?
Life Serial - S6-E5
Revealing mistake: In Jonathan, Warren and Andrew's van, whenever they're watching something on the monitors fed from their security cameras, you can see that the footage is actually pre-recorded due to the fact that the footage is being played through QuickTime media player.
After Life - S6-E3
Visible crew/equipment: When Dawn is possessed by the demon and breathes fire in the magic shop, in the bottom right corner of the screen in one of the shots, a metal tube can be seen blowing fire onto the set when it should be coming from Dawn's mouth. A hand can also be seen holding a blow torch, igniting the tube and then quickly pulling out of shot.
Visible crew/equipment: When Giles, Willow, Tara and Buffy (in Faith's body) arrive at the church in the armoured van, a camera is reflected in the van's back window.
Continuity mistake: When Buffy and Riley are in Buffy's room, Buffy holds Riley's hand with both of her hands and says to him, "Is there anything I can do?" But in the following shot she is holding Riley's hand with only one of her hands.
Revealing mistake: When the ubervamp is at the door of the Summers' home, you can see a black string attached to the inside of the door.
Chosen answer: He had larangitis and because of the shooting specifications they had to have him shoot the scene with a bad throat, they then re-recorded his lines and dubbed them. At various points during the scene and indeed the episode you can see him touch his throat or rub it.