Assassination

Obvious stunt-double (younger man, different face, darker/differently-styled hair and mustache, etc.

) when Killy jumps off the bike to avoid a rocket round.

Presidential inaugurations are in January but footage of the motorcade shows trees in full summer bloom and people in summer clothing.

When Mama One is taken from the helicopter into a car, there are several cars and a truck following.

In the next shot from within the car there are no cars at all to be seen through the back window.

When Ireland and Bronson's characters are being chased by Bracken in the Pickup truck they are shown to be on a two lane highway.

In the middle of the chase there is about one second when you see they are being filmed on a one-lane dirt road before they actually turn onto the dirt road.