(at around 1h 22 mins) Towards the end of the film where the woman rushes towards Alex and Alex slams the door, she is clearly wearing a dark blue top just as the door slams, however as she smashes through the door with the left arm and upper body, she is now wearing a white top.
(at around 31 mins) In one scene, Alex follows a trail of toys into Wyatt's room. She inspects his closet and behind her, the toy train turns itself on. Startled, she turns around to head downstairs. On her way out of Wyatt's room the toys are now gone.
The time tags - when Katie kills Daniel and Kristi - are not the same as in PA2. An example is when Katie leaves the house with Hunter in PA2, the time is 11:51:03PM; but here, the timing is about five seconds short and by the next shot, Katie and Hunter are outside with the time slot being 11:52:44PM. So, what took so long?
(at around 20 mins) When Alex shows Ben the footage from night #1, the Calendar icon in the OSX dock clearly shows a one-digit number (possibly 6, since that's the date it's supposed to be). However, when the shot changes to a closeup, the icon now says it's the 17th.