Continuity mistake: When Curly Bill is shooting up the town while drunk, he fires about 10 more rounds than his six shooter can hold without reloading, and still has a round remaining when he shoots Marshal Fred White. In the 1880 court hearing held after Marshal White's death, Curly Bill still had 5 rounds remaining in his pistol.
Plot hole: At the end of the film Woody shows what a nice chap he is by spending the 'tainted' million dollars at a charity auction. He's just made his problems much worse - he paid his solicitor a large fee to arrange the deal, so he hasn't got a million in the bank. That cheque is going to bounce so fast it will crack the plaster on the roof of the bank, and bouncing a million dollar cheque is a serious criminal offence in the US. (There is no way enough interest could have built up to cover the difference, either).
Visible crew/equipment: Between the beginning of the movie and the end of it inside of Jesse's shop when the camera is facing the entrance and Jesse's desk look real closely at the window reflection in the playroom with the children and you will a see a man wearing a white shirt holding a camera prompt against her desk.Kevin Brown
Factual error: While in the convenience store, watch the arcade screen the punks are playing, they are getting very excited about the game, however anyone who has played StreetFighter 2 will notice that they are merely looking at the demo version and even the words "insert coins" are displayed on the screen. Still, if it makes them happy...
Continuity mistake: When Sam is making grilled cheese sandwiches with the ironing board and iron, he finishes one sandwich and places it on top of another on the side table. After Joon's explanation of cheese and culture the camera cuts back to Sam placing another finished sandwich on the side table on the same place that he placed the first but there is only one sandwich there where there should be two.
Continuity mistake: When the female owner of Beethoven's girlfriend (Virginia or something like that) tells her boyfriend (Floyd) to put the leash on the dog, he goes to do so but when you see his hand clip the leash on, the shot changes to a woman's hand clipping the leash on (the nails are covered in nail polish).
Revealing mistake: In the final scene when Annie and Sam are exiting the observation deck coming towards the elevators, the New York skyline backdrop which should be visible behind them is missing, and the entire sound stage wall can be seen beyond the observation deck safety railings instead. 'Although the exterior and lobby of the Empire State Building, 350 Fifth Avenue at 34th Street, are the real thing, a slightly larger replica of the Observation Deck was built in a hangar at Sand Point Naval Base on Puget Sound just northeast of - where else? - Seattle.' https://www.movie-locations.com/movies/s/Sleepless-In-Seattle.php. (01:39:35)
Continuity mistake: In the scene where Maggie goes to the restaurant with Bob, he offers her the case where the weapon is. Bob says, 'It's loaded'. Close inspection shows the clip chamber is empty (not loaded), and a cartridge clip is positioned beside the weapon in its tailored slot in the custom case. Maggie closes the case and says, 'I don't understand.' After Bob explains what she is to do, then leaves, Maggie opens the case again and suddenly there's a clip in the weapon (loaded) and another one beside it. The weapon was not loaded when she looked the first time.