Revealing mistake: When Ernest's jack flies out from under his truck it breaks the back windshield of the mayor's car. Watch closely and you can see the glass shatter before the jack makes contact with it.
Revealing mistake: At the end, when Trantor shoots flames out of the ground to stop the crowd, the ground is split apart wide enough for the flamethrower to shoot flames out. The ground never shook apart or anything, because they show the ground before the flames shoot out and it's already split.
Revealing mistake: When Trantor scratches the roof of the truck trying to get to Ernest, you can see that it is cloth ripping instead of the metal on the roof.
Revealing mistake: When Ernest picks up the hedge clippers in the back of his truck to attack Trantor, you can see where it is supposed to be sliced off at before Trantor cuts it off.