The narrator mentions they arrive back in San Francisco in early October, but in the document (prepared by Grisby) that Wells signs verifying his killing of Grisby, it is dated August 9th, supposedly the next day.
At the beach picnic, whilst O'Hara is talking to Bannister recounting the shark story, we see Bannister continually swinging back and forth in a hammock, but in a couple of shots from different angles, the hammock is suddenly completely stationary, then suddenly back to a swinging motion.
When Grisby is toasting to the murder plot with O'Hara, he holds up a glass that is 3/4 full of beer. When he raises the glass up to drink from it, it is almost completely full.
In the courtroom scene, Mrs Bannister's maid is sitting behind her when she is called to testify, but in the next shot, when she gets up, there is a man sitting there.
When Mr. and Mrs Bannister are talking on a bench in the courthouse, he is taking a drag on a cigarette. A moment later, the cigarette is resting in his hand on top of his cane.
When Michael first sees Elsa in the carriage in the park, her first close-up shows a static background, even though the carriage is moving at the time. The insert is clearly an edit from the later close-up - after the carriage has stopped and before she accepts his offer of a cigarette.
When Mrs. Bannister is lunging for the exit in the mirrored room, the "broken glass" in the foreground stays in frame as the camera pans to the right, spoiling the illusion of a cracked window.