The nun says there have been only twenty-three miracles at Lourdes (up to the time In which the film is set). There actually had been sixty-two. UPDATE: At some time prior to April 2024, the filmmakers must have changed the film to correct this, because the line now states sixty-two.
At one point in the film, Maggie Smith's character is in a wheelchair which is very clearly a modern make and style vs. the 1960s era the film is set in.
The characters are said to live in Ballygar. Yet, Lily walks to a seaside shrine to the son drowned in the sea. Ballygar is more than 30 miles from the sea.