14 minutes into the movie, when Frank Chambers and Cora Smith begin dancing to a rumba record that Nick Smith puts on the jukebox -- as the pair are slowly dancing towards screen-left, Lana Turner's face breaks-up suddenly into a huge broad smile. Her eyes are looking into John Garfield's' the whole time. Turner tries to control herself as they move into a shadow, but by the time she comes out of the shadow she is obviously laughing at something that John Garfied has either whispered, or maybe a face that he has pulled at her [as the back of his head is towards the camera we do not know for sure?]. But Lana was definitely not supposed to be laughing because in the next cut the pair both have extremely serious faces again.
When Blair, Sackett and Frank are looking at the stepladder and see the dead cat, its body is shown next to the further foot of the ladder. In a later shot from a distance, the cat's body appears between the feet of the ladder.
When Frank and Cora first leave Nick, Cora falls in the dirt to avoid being hit by a car. All she lands on is her bottom. But the dirt keeps changing it's location in different shots, being sometimes on her shoulders, on the front of her skirt, completely gone when she sits on the suitcase, then obviously applied to her bottom as they are returning to the diner.
In the first scene in the new beer garden after the trial, Frank is shown holding a tray with 3 glasses on it, except he is holding the tray at such an angle that the glasses would obviously slide off if they weren't glued in place.