When she shows the police officer the footprint , the computer keyboard keeps disappearing between shots.
When Ruth looks at her porcelain cupboard, the plates are piled on top of each other, but none of them are even slightly broken. This is not possible in the case of theft, especially cups that seem to have been intentionally placed on the floor. But then she collects the pieces of the broken plate that did not exist in the previous scenes.
While the conspicuous placement of the Catan game in Tony's house may at first seem out of place for a loner like him, and therefore an error, it more likely represents his innermost hopes and plans for a life with stronger social connections. He dreams and prepares for a day when he will have enough friends to play the game. Its presence the first time Ruth enters his house is both forlorn and optimistic.
(Possibly intentional) Ruth drives a Pontiac, but the hood scoop has "Chevrolet" stenciled on it.
This film is set in Virginia, which requires license plates to be displayed on both the front and back of vehicles. In the film there were no front license plates.
When Marshall jumps in the boat to chase Ruth he forgets to unhook the boat. It never shows him get out and the next scene he is already in pursuit.