A lot's been made of Muller (Paul Henried) scarring himself on the wrong cheek in his attempt to impersonate Dr. Bartok. However when he actually does it, he does prepare to cut himself on the left cheek, but when he applies the bandage to help his face heal, it's placed on his right cheek, and subsequently, the scar stays there for the rest of the movie.
Pre-WWII stock footage of the taxicab that is taking Paul Henreid to the ship includes shots of a taxicab much older than the one which finally pulls up at the dock.
When the gang is driving away from the casino hold-up, it appears the trailing car is hit three times in the rear window. (Actually it looks like someone is throwing paint balls inside the car at said window.) In the next shot of the car crashing into the lamp post, the car's rear window has no such defects.
The position of the file that John Muller was reading in Dr. Bartok's office file cabinet changes position between shots.
When John is pumping gas, the pump shows $1.00's worth - but at 25 1/2 cents per gallon as indicated, the pump should read 3.9 gallons delivered, but it reads 4.9 gallons.
When Muller is looking over the doctor's bank statement for the month of February, 1948, several entry dates fall on a Sunday when the bank would have been closed - February 1, 8, and 15 to be exact.
When Muller is looking at the broker statements of the stock that had been sold by the doctor, the one for Black Oil Co. shows 650 shares sold at $125.50/share which totals $81,575. However, the total column on the sales slip begins with the digits 12.
During the scene at the gas station where Paul Henreid is adding gas to a car, the acoustics are wrong for an outdoor scene. This scene has obviously been shot on a set not actually out of doors. Even his footsteps as he walks around the car have the sound of studio set floor.
Evelyn says her hairdresser is at Wilshire and Laurel. Laurel Street in LA doesn't cross Wilshire Boulevard. In fact, it's miles away. Also, there's no Belmont Drive in Sherman Oaks, as listed on a patient's file. The closest Belmont is an Avenue in the Echo Park area.