Deliberate mistake: When Phil wakes up at 6 AM, it's already bright outside. At 6 AM in February, it would still be pitch-dark.
Deliberate mistake: In the scene where Sam is swinging from the hospital window, you see him first from the inside. Now he is obviously being pushed (from a crew member) so it looks like he's moving back and forth smoothly. However, when seen from the outside he couldn't be pushed and so when swinging by himself, he was actually bouncing off the walls. Inside this would have been seen. Also, inside it seems that the sky is clear, though outside there is a tree by the window.
Deliberate mistake: Gray's rental car just happens to be the one car out of the hundreds in the parking garage that the bad guy chasing Gray and Darby crashes into, setting off the bomb he had placed.
Deliberate mistake: When Wyatt comes out of the Oriental and joins his brothers in the street to tell them he's acquired a quarter interest in a game, a herd of cattle is passing them in the street but there's no dust kicked up by the cattle, when in reality there would be a lot of dust on a dry desert street in Arizona.