Revealing mistake: When the house is burning at some points we can see the flames inside the house are fake. If you look at the window you can see some of the flames are actually outside the house. The flames are just reflected in the window. (00:20:35)
Revealing mistake: It is really obvious Jackie Chan was on a wire when holding onto Roy at the end. His body floats and moves in a very unnatural way.
Revealing mistake: The car that falls into the water has a surprising lack of damage after such a long tumble.
Revealing mistake: When walking across a curved path, you can see Judy step off the floor where he was supposed to walk.
Revealing mistake: When Gypsy tries to hit Helen with her weapon, she misses and hits a table instead, causing one of its leg to break off. However before the weapon even hits the table you can see the leg coming off from the table; obviously being pulled off.