At the final battle where Julien takes 2 of his crew members as dogs with chains, he once wears his jacket, the next shot he stands there without it and so on.
During the Game Night scene at NYU, Moose and Camille win a round by using the clue about their 5th grade teacher. Camille also says to her friends that they have known each other "for forever". But later in the movie, when Moose and Camille are making up, Moose hears the song from the ice cream truck and says it is the song they met to freshman year at MSA.
During the second battle at the house of Gwai, the floor changes from hard flooring to carpet after Moose releases the water.
In the Samuri's final dance when Julian takes two of the dancers as his dogs you see him wrap the chain around one of them's necks then the camera changes angle and you see him do it again.
Before the first dance battle Moose drops his backpack, but when he escapes with Luke it's back on his back, and then when they stop running, it's missing again.
During the first training montage where Luke and Natalie are doing the martial arts sequence, Luke's physique changes from being muscular to lean and skinny (obvious stunt double).
When Moose, Camille and Moose's mother and father are walking to the University, she wants to make a picture of Moose and Camile. When she points the camera at them you see that the display of the camera is turned off.
The 5 dollars Moose hands over to the ice cream man is clearly a fake
In the final battle/dance scene, Julian goes in and out of the frame. In almost each frame he is wearing a jacket and then in the next, he is in a muscle tee.