Continuity mistake: Throughout the movie, Alan Arkin is carrying in his breast pocket a Cross Chrome pen to write messages with on his pad. (He is a deaf mute.) But in the scene where he is on the porch with Sondra Locke and he is drawing a picture for her, he pulls that pen out of his pocket, yet when the scene cuts to a different angle showing him actually drawing on his pad, it is a thick, black felt tip pen. (01:25:00)
Continuity mistake: The ford transit van used by the demolition men Ron and Mr Perry changes between scenes from a long wheelbase van reg no. KGX107D to a standard van reg no. OYO576F.
Continuity mistake: The girl named Why is in the bathtub. Frédérique brought her a cup of tea that she indignantly put aside because it had an excess 1/2 sugarcube. She put the cup to the edge of the tub with the spoon facing one direction, but during the conversation the spoon turns 180° on its own during a cut. (00:07:40)
Continuity mistake: During the opening credits, Charles Bronson is walking along the pier, carrying his bag over his left shoulder. He stops in a separate shot, grinning at the camera and tossing the highball glass he was carrying into the sea (as soldiers normally do). In this same shot, he switches the bag to his right hand. Back to the previous angle, and Bronson is again walking with his bag over his left shoulder, like nothing happened. (00:01:15)