When Jo, Brad, and Toni are riding in the cab together for the second time, Toni is wearing a mink stole. But in the shot where she exits the cab, suddenly she's not wearing the mink stole anymore.
When the waiter carrying the cake slips and falls, he supposedly does so because Toni Gerard dropped her lipstick on the floor; however, the waiter does not actually step on the lipstick prior to falling.
In the restaurant, after Jo Ainsley sends her note to Brad and leaves, and he is explaining to Toni about Jack Ainsley's death, the top of a man's head can be seen appearing to move across the mantle. It is someone walking behind the fireplace/mantle.
Mic shadow visible in upper left of frame as Milland and Goddard step into elevator.