When Louise goes into the pond after stripping to bra and panties, her panties are tan or light brown, yet in the underwater sequence they are black.
In some shots, Ron Perry as Arthur has two good arms, but in other shots, his left arm is in a cast.
When Billy is holding the candle whilst talking about being stressed, the candle has been smoldering with quite a bit of smoke, but the next shot shows the candle is lying on the table and there is absolutely no smoke.
At the wedding, Caleb removes his tie whilst talking to Kane. His shirt alternates between remaining buttoned to the neck and being open at the neck between camera angles.
In the movie's latter half, Dr. Caleb enters a work shed and discovers the body of Louise and the lifelike Kathleen doll. Carefully picking up the doll, he closes the shed door, and immediately in the next scene is shown walking with the doll in his arms and a cigar in his mouth.
In the end credits, Guinness Brewery is misspelled "Guiness".
(at around 50 mins) The main characters are having tea on the castle lawn. In the background a man appears on the left of the screen as if about to walk across the lawn; instead, he hesitates and ducks out of sight and disappears behind a hedge.
When Billy and Kane are walking around the pond, the boom mic falls into view. A little later, the shadow of the boom mic operator is visible on Kane.
When Billy and Kane are talking by the pond, Billy mentions that they always hold black umbrellas, but at the funeral, Lady Haloran and Billy are holding black umbrellas but Richard is holding a white umbrella.
When Dr. Caleb tells the maid to count the silver, Richard says it's one of his most astute "diagnose" mispronouncing "diagnoses".
(at around 6 mins) When Louise is typing a letter to Lady Haloran, she types "willbe", failing to put a space between "will" and "be".