Revealing mistake: When we see a vision of Child-Alyssa walking down the street with a sort-of vortext behind her as the cult-members flee, watch closely and the entire shot is comical. All of the extras are barely moving at a jogging-speed despite supposedly running for their lives from her. Several are visible running towards her direction or even directly behind her despite supposedly fleeing from her. Several extras veer off to the side before exiting frame even though there are buildings on either side so there's nowhere to go. And several others still are visible running left-to-right or right-to-left from either side of the frame, again despite there being buildings on either side. Obviously all of the extras were filmed in front of a green-screen being told "just run around a bit" and then added to the scene. The shot makes no sense if you pay attention.
Revealing mistake: When Picasso removes the first finger from Fan Yau Lee's hand, you can see that there is no blood on the instrument used.