The bread and milk the killer tosses inside the front door of the villa disappears when Jane goes to door.
When the guy riding a motorbike flips over and lands in his back the mud, he has mud on his back and chest and face before he lands in the mud.
When professor and student talk, they are walking through the church. In two consecutive shots, you see them walk and then stop at a point they already passed.
When guys are walking through the night, one of them kicks the can on the ground. There is no way that can would end up where it's shown it went, because we can clearly see where he kicked it.
Stefano's pose is changed in 2 consecutive shots when he falls down.
You can see the first victim still breathing after being killed.
Near the end of the film, a flashback scene shows a boy slipping while reaching for a doll. Next there is a cut to an obvious dummy being thrown at least ten feet clear. Then it cuts back to the prior view and the boy is lying very near the base of the cliff.
During the scene where Suzy tries to signal for help using a compact mirror, the camera crew is clearly reflected in the mirror as she jiggles it around.
In the train, the camera operator's arm is reflected in the carriage door. Also, when the man enters the train carriage and closes the door, the camera crew and boom pole are reflected in the glass.