Other mistake: On pursuit of one of his conquering strategies David comes into the tennis hall where his present belle Gretchen is waiting. He looks around and calls out for her, although the full moon is shining through the windows and she is standing in the middle of the court, quite visible in her white dress. (00:06:35)
Continuity mistake: Sabrina arrives at the Larrabees' party with a black, lacy handkerchief in her hand. When she starts dancing cheek-to-cheek with David, the handkerchief hangs down gracefully from their joined hands. The camera briefly cuts to his mother and his supposed-to-be mother-in-law, and when it cuts back to them the handkerchief is stuffed into her glove. (She could have done that in between, but then she would have had to let him go, and the intimate way they are dancing doesn't suggest that at all.) (00:44:15)
Factual error: When David talks to Linus about the consequences of calling off his engagement with Elizabeth he says that their father would take to the bottle and smoke six coronas. Throughout the movie the old Larrabee smokes one churchill after another, but not a single corona, which is significantly shorter than a churchill. (01:02:05)
Continuity mistake: Sabrina's slightly unruly hairdo is a continuity problem throughout the movie. This is especially noticeable in the sequence which starts with her calling Linus in his office from the lobby, and ends with her leaving the office after learning about his plot. When she makes the call her bangs are full and fluffy, but in the office they look rather cemented and change from shot to shot. (01:34:55)
Other mistake: In analogy to David's mishap with the champagne glasses old Mr. Larrabee crushes an olive jar when he sits down. However, in contrast to David he puts the jar into the front pocket of his pants, and olive jars don't break even if you sit on them (remember what he did to one when he tried to get the last olive out.). (01:46:55)
Other mistake: At the beginning, when Sabrina describes the Larrabee family, she says that David is listed as a $600 deduction on Linus' income tax return. Two problems: 1) Shortly after Sabrina goes to Paris, Linus is shown sending David a memo to remind him that he is a junior partner in the family company, and is eligible for retirement - based on his one year with the company. 2) Both David and Linus still live with their parents. If David could be claimed as a dependent, I should think it would be by his parents.
Continuity mistake: When Linus goes to the tennis court in place of David to meet Sabrina, he pours champagne for Sabrina and himself and they start to dance, each holding a glass. The next shot the glasses are gone from their hands. At first glance I thought glasses left set completely. Upon further observation noticed they are on the floor under the tennis net.