At the end of the film, when Willy is running after Peter and stops, there is clearly nothing at Willy's feet. Later, after being told "Swing Heil", he grabs an umbrella on a wet poster at his feet that clearly wasn't there before.
In an establishing shot just after the Nazis steal the radio, the rear half of a Vauxhall Wyvern can be seen parked on the street; this car was not introduced until 1948.