During the rescue in Act IV Kuryakin goes back and forth from being barefoot and wearing shoes.
Solo cuts a peep-hole out of the box to his right. When the bad guys discover the hole, it's now on Solo's left.
Although the car chase is supposed to be in London and British style phone boxes are seen in the background, an American style fire hydrant is seen on one of the corners.
For the street scenes set in England, there were American style cars with left hand drive driving on the wrong side of the road.