When Sarah looks at her mother's picture in her bedroom, the pink 8-Ball "Date Ball" is to the picture's left, next to the stack of books. In the next shot, it's clearly moved to the shelf above the books. Returning to the close-up of the picture, it's next to the books again. Next shot, it's again up on the shelf.
When the characters are looking in the High School Yearbook for a picture of Beau, his name is listed first in the column of names, indicating that his picture would be first in the row of pictures. However, his picture appears last in the row of pictures.
When Sarah and Jeff have an argument near the end, you see Sarah go into the elevator with a jacket on. The scene goes to her crying in the elevator, no jacket.
When Sarah meets Beau's 'son' Blake, Blake says he has just returned from Asia to his father. As Beau moves towards Sarah after this line, Blake can be seen behind Beau scratching his face. The shot moves to Sarah then back to Beau and the exact same shot of Blake scratching his face is used.
When Sarah and Beau are sitting on his car overlooking the vineyard, Sarah's hair is alternately tucked/not tucked behind her ear.
When Sarah and Beau are in his plane going down the runway, as a pilot, Beau would be wearing a headset to communicate with the tower or with air traffic control, but he isn't. However if we assume he has a private airstrip there would be no tower and he may have chosen to put on his headset later.
In January 1997, Jeff jokingly tells Sarah that his family is like the movie "Titanic", and goes on to talk about nude sketches of himself - a specific reference to Titanic (1997) as opposed to any other Titanic movie. The movie wasn't released until December 1997. However, the nude sketches scene was used in advertisements some time before the movie release, so it is barely plausible for Jeff to make this allusion.
In the drive to the plane in Beau's Mercedes, the gear shift selector is in the park position.
When Sarah and Jeff are walking through the airport you can see the scenery through Sarah's head for several seconds.
There is an ad for "World Cyber Games 2004" on a cable car when the date has been established as January 1997.
As Beau and Sarah are standing out front of the conference center after their initial meeting a cable car passes through the frame with an advertisement for a 2005 model Samsung flip phone on it, despite the established time frame of January 1997.
When Sarah is nearing her cab at the airport, there is a mix of yellow Ford Crown Victorias present, some of which feature the updated 1998 model design, which would not have been seen in January 1997.
When Sarah and Jeff are arguing at the ball, the sound and movement do not sync up.
When Sarah and Jeff are going up the escalator on their return to the elevator, there are reflections in the upper 25% of the frame.
Someone says Richard Dreyfuss' first film appearance was in The Graduate (1967). In fact, Dreyfuss appeared in Valley of the Dolls (1967), released a month earlier.
When Sarah wakes up at Beau's house she asks him where they are, Beau says they are in Half Moon Bay, an hour south of the City. Half Moon Bay is actually only a half an hour away from San Francisco.