When James refuses to eat, the cereal box changes places between shots.
When Gordon is trying to teach Spot how to be a dog, he throws a red ball that hits Spot and rolls away. In the next shot, Gordon has the ball again.
When Agent 11 is in the park, hiding behind the tree, he has a collar on, but when he's running away, he has no collar.
The movie takes place in Seattle. When Gordon looks after James, he asks where's his school and James said it's summer but Stephanie claims that there was some freak blizzard and it's unknown where she went on her trip. She might've went to Alaska.
The scene in the pet store takes place at a Petcetera location. The movie is set in Seattle, Washington. Petcetera is a (now-defunct) Canadian chain of pet retail stores.
When Gordon and James take Spot to the beach to try to make him catch a ball but when they leave to go to the pet store to get the dog an incentive. Gordon has a regular pickup truck but when James runs away after the FBI takes the dog back and Gordon searches for James, he drives his mail delivery truck to look for James.