Buffy is waiting outside the crypt when the vampire with glasses steps out. This guy is someone who works with Spike and Drusilla. When he steps out the camera is from behind her. It swaps around a couple of times until you can see a vampire coming up from behind her (camera infront of her) while she is still talking to the vampire with glasses. The camera goes from behind her shot again with the crypt in view as she fights this new vampire. The vampire with glasses has gone now but you should have actually still seen him there or at least leaving.

Also in this episode when one of the evil guys from the order of "terrakka" steps of a bus you can see "watch your step" signs on each step. When the shot goes between his feet they're gone.