When the beer barrel is being chased the sign above the cab turns around. It says Reid's Stout on the front & Watney's Ale on the back, but later in the chase it is the other way round.
When Hugo Dill is outside the Uralian Legation building, Frankie Mayne and Raymond Courtney walk down a small set of steps two times out of the building opposite.
When the beads from the necklace are spread all over the ice, the skaters wouldn't fall over as they do as they are skating on blades which wouldn't make contact with the beads.
When the heroine tosses a villain out the window, you can see he's being held up by a wire. Then, as he goes through it, the stuntman accidentally destroys the paper "wall" over the window.
When Frankie (Belinda Lee) carries the dead Stumpf (Denis Shaw) over her shoulder to her car, it is obviously a dummy.