When Dawn closes the front door at 14:10 and the view cuts from interior (studio set) to exterior (actual house), the hardware and panes of glass in the door are an obvious mismatch, and the sidelights change from frosted glass panels (studio) to clear, mullioned glass with curtains (house). Also, the staircase visible behind Dawn in the exterior angle does not match the one on the set.
At 39:30, as Tara is packing up Willow's magic supplies, the camera angle changes and her left hand, which was palm-down holding a plastic bag, is suddenly palm-up holding several sprigs of herbs.
Spike's reflection can be seen in mirrors/windows at three times: 18:28, 41:00, and 41:18.
As Spike walks toward the front door at 40:53, you can see part of a lighting instrument at the top edge of the frame, just left of the door.