When Nick is hit by the car on the night he "died",
the car side-view mirror was not damaged. It was still attached to the car after Nick was hit. Later, the police find the mirror broken on the ground at the scene of the crime.
When Annie is looking over Nick's photographs, the two of them mumble about "July fourth weekend." As this film is set in Burnaby, BC, no resident would talk about "July fourth weekend", rather July FIRST weekend, Canada Day weekend or perhaps Dominion Day weekend. Canadians do not celebrate the fourth of July.
Nick (to test if he was alive) takes a shotgun from the rack, steps out of view and discharges the weapon. The mistake is that the shotgun he took from the rack was a double barrel shotgun but you hear the sound of him "racking a round" as if it was a pump shotgun just before pulling the trigger.
When Nick was walking home from the party, he kicked over a big trash can and a trash bag. The big trash can landed in the middle of the street and rested on one of its handles. The very next close up shot of Nick, you can clearly see in the background that the trash bag and trash can are back on the curb.
The car hot wired outside the jewlery store is a Mercedes Benz with an ignition system that cannot be started in any way at all without the electronic key. This system is called DAS, Drive Authorization System. There is no way they could have started that car without the key to 'authorize' the starting of the vehicle.
The character of Nick has planned to study writing at 'The Royal Academy' in London. The Royal Academy is/are a group of distinguished painters/artists. The Royal Academy is also a building which hosts art exhibitions. Not a place of study for writers.
When the police are rushing to the dam, Detective Larsen asks Detective Tunney how long until the dam opens. She says 15 minutes. Yet, she waits until they are standing on the dam to use her cell phone to call to have the water shut off.