in the Lido Plunge swimming pool scene Mature is holding cigarette in right hand. Cut to close up, and it's now in his left hand. (He then flicks it away onto the pool deck without hesitation, despite everybody being barefooted.)
When Cornell asks Christopher for a lift he tells him to drop him at 58th and Madison.The car pulls up in front of brownstone apartments. There are only stores on 58th and Madison in NYC, no brownstones.
When Vicky Lynn's dead body is on the floor, and is being examined by Frankie, Jill walks in the room and the camera begins to quickly dolly up. All of a sudden, Vicky starts to quickly roll away as if to get out of the way of the camera path. (They show the same revealing mistake in the movie's trailer.)