When David is "discussing" his engagement to Elizabeth with Linus in Linus' office, the newspaper moves around on the desk between cuts.
When Linus makes the phone call in the car to begin buying Tyson stock, the view out the back window is the Long Island shoreline. When it cuts to Fairchild listening, the view out his window is buildings. When it cuts back to Linus, it's the shoreline again.
When David and Sabrina are discussing the dancing lessons at the end of the movie, David raises his glass of champagne. The scene cuts to Sabrina and back to David, and his hand is in a different position on the glass and the color of champagne is lighter than before.
David puts olives in the martinis twice
When David is confronting Linus in his office, David enters, Ron and Ron leave, David slams the door. When he does this Linus leans back in his chair. The camera pans back to David for a line and then returns to Linus who is still leaning forward at his desk, not having had time to get back to that position
Linus leaves the first party early because he needs to check on the Tokyo markets before they close. But Tokyo financial markets would close at 4:00 AM or 5:00 AM New York time. It is clearly not that late in the evening.
On the third evening after the accident, David says "the stitches are coming off tomorrow". Removing stitches so quickly is not realistic.
Towards the end of the movie, Linus is stuck in traffic and must run to the E60th St. Heliport. He is shown running from the car without his bag, yet he has it when he boards the Helicopter.
When Linus is rushing to board his helicopter, Sabrina's father, apparently relenting and giving Linus his blessing, tells him the address of Sabrina's Paris apartment. The apartment that Linus arranged.
When David runs into Sabrina after picking up the Picasso, you can see the door to the traffic light controller box is wide open indicating that someone is controlling the traffic for filming. (If the box was open legitimately, the operator would not leave it unattended.)
As Sabrina rides the train home from New York, she is photographed through the small vertically-rectangular windows of an old fashioned commuter train with sharp corners. Across the aisle behind her, the windows on the opposite wall of the train are broad and horizontally rectangular with rounded corners like a modern commuter train.
Linus is shown looking at a fishing village (Menemsha) on
Martha's Vineyard through a camera lens. He pans across until he comes to a lighthouse. There is no lighthouse in Menemsha. The lighthouse shown is in Edgartown, clear on the other side of the island (20 miles away).