When Zack runs for the door in fear, he pulls of the doorknob, trapping him in. In the next shot, the door has miraculously opened even though it was locked, and then in the following shot when the door is closed, the doorknob is back on.
When London finds her gold purse in suite 613, she places it on her left arm just as the noise at the door scares her, but when Cody tries to jump into her arms the purse is on her right arm.
When the closet opens revealing the "skeleton" and it starts dancing you can see Arwin in the background making it obvious that everything was fake.