Audio problem: When Angel is having a go at Danny in the rain after Tim Messenger has been murdered, there is a shot of Danny over Angel's shoulder. In this shot you can see Angel's mouth isn't moving, but we hear him still shouting at Danny.
Audio problem: When SGT Angel is at the train station with his Japanese Piece Lily and is waiting on the bench, we see a British Rail Class 165 leaving, however the speed the train is going at is too slow for the matching traction sounds (the sound of the train going over gaps in the rails). Also the rear of the train does not match a Chiltern Railways 165, it looks as if it has been edited (although the number reads 165007). Later on, we see Angel almost dropping off to sleep and a fast train comes in and blows the horn, the horn sounded does not match the horn that would come from this type of train, it sounds more of what would come from an EMU version (possibly 365 or 465 Networker).
Chosen answer: In the pub Danny demonstrates using a ketchup packet to simulate stabbing himself in the eye. Later in the film he returns Nicholas Angel's notebook, hiding a ketchup packet in it. He stabs the pocket with the notebook, causing the ketchup to leak and simulate blood.