At the 25 minute mark, the three visitors are trying to escape the convent. They reach a flight of stairs and decide to explore the floor below. When they walk down the stairs, the walls look to be from the actual building, but once they reach the floor, the shot changes and a worn-down wall is shown in the background. Some contemporary-era bricks are exposed, which do not match the historical background.
Around 8:13, when the first monk opens the doors for the three visitors at night, some shots in which the faces of the three are shown, the monk's hand is on the foreground, holding a lamp. Even though the lamp is shown in previous establishing shots as lit, it is not in this one. Furthermore, the lighting on the visitors' faces come from a different angle and is diffused. The lamp's light would be quite hard and more frontal to them.