When Picard, Data and the village lady enter the hologram in the lake, They are ambushed by a villain. The villain is shot and falls from the top of a building. When he hits the ground, the sides of the mat placed to break his fall pop up into camera view.
To the person who said not to sweat small mistakes . . . this site is about picking up on small mistakes. I don't know if it's there or not, but this is a forum designed for sweating the small stuff