After the party when they are hiding at the school, Thomas tells Dax (The main person recording everything) he'll be fine and to go home, however later footage is shown of Thomas talking to his dad. This footage shouldn't exist since Dax left and no one else was around at the house afterwards.
Thomas rescues his dog, Milo when a group of party guests tie him to a set of balloons and send him afloat, Thomas is heard yelling "That's my
dog". Kirby remarks that she should record the event. Seconds later she shows Thomas the recording inside the house and you can hear Thomas yelling "That's my dog" which he said before she started recording.
Before party starts the boys are in Thomas's bedroom and his Dad calls for Thomas. Thomas and Costas run out and there is no skateboard between mirror and piano. Then when Dax films himself in that mirror you see the piano and a skateboard appears.
Before the party when Costa and Kirby are seen playing Mortal Kombat, it is clearly indicated that Kirby is winning and is playing as the character Reptile. However, a few moments later when she says she has won, we see that Reptile has lost and as been knocked off the field.
Near the beginning of the movie, while in the van, the driver hits the brakes to have the kid in the passenger hit his head. The thing is that he would have been forced forward into the dashboard not backwards into the head of the seat.