At the very end of the movie when the camera is behind Katie as she reaches up to touch the front of Hubbell's hair, he grasps her wrist with his right hand. When the shot immediately switches to behind Hubbell, his hand is not on her wrist.
At the end of the movie, Barbra Streisand and Robert Redford embrace. He's wearing a trench coat with the collar up. In the course of the embrace, shot from behind Redford, Streisand's gloved hand moves down the back of his head, ultimately flattening the collar of the trench coat. In the next shot, face-on to Redford, the collar of the trench coat is back up.
At the end of the movie, the thick collar on Katie's coat is alternately up/down between shots.
Near the beginning of the movie, as Hubbell is dancing with Katie, you can see her pearl ring on her finger go from the pearl centered on her ring finger to the ring turned and the pearl is down next to her little finger. The pearl is then centered again on her finger. It also looks like the ring changes size from fitting her snugly to being loose then fitting snugly again.
(at around 1h 10 mins) When Hubbel is at Katie's apartment, he thumps the frame located close to the window and places both hands on his hips. In the next shot, Hubbell's left hand is placed on the frame.
When the radio announcer refers to the time of Franklin Roosevelt's death, he says it occurred at 5:45 in the morning. President Roosevelt died in the early afternoon.
At the beginning of the film when there is a montage that depicts how athletic Hubbell Gardner is, there a shot showing a birds eye view of him throwing the discus. He throws the discus out of the throwing circle traveling from one side of the circle (9 o'clock) and sees him release the discus at the other side (3 o'clock). The correct position for releasing the discus is clearly marked on the circle at the 12 o'clock position.
In the extended cut, toward the end of the film, Katie drives her convertible through what is supposedly the UCLA campus, where she sees a young activist giving an inspired speech, reminding her of her younger self. This was actually shot at USC, in front of Doheny Library.
When the reporters meet Hubbell, Katie, and the others at the train station as the group returns from the Washington HUAC protest, one of the reporters has huge, 1970s-era "mutton chop" sideburns, totally out of place in the scene's 1950s time period. However, mutton chop sideburns date as far back as the mid-nineteenth century so this style of facial hair is not anachronistic.
In California, Katie is holding a "hot" pot and offers it to Hubbell. He takes a spoonful and notes that it is, indeed, hot. However, moments later, Katie is holding the bottom of the pot with her bare hands.
In Katie's apartment the first time Hubbel visits, Katie prepares hot water for coffee. As she leaves the kitchen, it is clear that the top of the kettle is on crooked. As she enters the bedroom where Hubbell is sleeping in the bed, the kettle starts to whistle which startles Hubbell. The kettle would not have whistled with the top lop-sided.
In the final scene where Katie and Hubbell meet in front of the Plaza Hotel, modern NYC street lamps (of a type not introduced until the 1960s) are visible in the background.
In the opening scene, where the movie marquee is shown displaying Counter-Attack (1945) starring Paul Muni and Larry Parks - that film wasn't released until April 1945. However, The Way We Were starts in the spring of 1944.
In the opening scene, the movie marquee is also shown displaying the Marx Brothers film "Go West", which opened in December 1940, a year before the U.S. entered WWII.
When Katie and Hubbell are meeting the group shortly after President Roosevelt dies, she makes her "meeting up every 5 years" comment, after that she says to Hubbell "What are we doing here?" When she says that, her lip movements don't match what she's saying.
At the beginning of the movie, Katie walks into a bar with Bill. They agree that Katie will have her usual, Dubonnet on ice. Bill disappears for a moment, then returns with Katie's drink, which has absolutely no ice.
At the dance, Frankie offers Katie some gin from a bottle, Katie then asks if the drink is bourbon.