When Giacomo exits monsignor's room after he tells him he has a fever, he opens another door and it's clearly light in that other room, but when he enters it, it's dark.
Giacomo is supposedly carrying a lit candle when he goes to monsignor's severed hand after unsuccessfully waking him up, but in the
shot where he is walking to it, there is no lit candle in his hand.
When Giacomo notices a note in the chest with the candles, position of the candles is different than in the previous shot where he picked one up.
When Giacomo's guide raises the chandelier and reveals all the books in the bookshelves, pigeons fly around the room, but they were
not present in the room in a previous shot.
There are two cases in the movie where men are cut with sharp objects, but both times it's obvious that no real cut was made and that only blood (fake blood) is applied.
Obviously a fake bat used in all of the scenes where one is present.
When Giacomo is peeking in the room where he sees two women lying in the bed, it's obvious it's a photo and not live image.
Dead man can be clearly seen moving his eye when Giacomo and his guide check him.
Obviously fake eyes on a man lying on the church floor surrounded by candles near the end of the movie. Also apparent when he appears in front of Giacomo for the first time.
When Giacomo and his guide enter monsignor's residence, a guide can be seen and heard trying to light a candlestick with two candles and it's heard he succeeded offscreen, but when he is shown, both candles are lit. He wouldn't have time to light the second one the way he did the first one.