Sam tells Karla, "four across looks like 'beets'", but, when Michael looks at the puzzle, four across is filled in and there are only four spaces, not enough for Sam's suggestion.
The Cadillac is clean when Fi arrives, but it is covered with mud when she pulls branches from the front grill, then it is clean again.
Michael drives backwards through some bushes. When Sam sees his car, the left tail light is broken, yet, just after Michael clears the bushes, it is still intact.
When the police officer picks up the planted automatic weapons, he does so with his bare hands, without gloves. This would be a fatal mistake for any real police officer, as it would compromise any fingerprint evidence that could be on the weapon.