The second time Noah visits Max at his job when he travels back to 10/31/2014, Max is wearing a different outfit than he was the first time Noah visited him when he went back in time.
At Avery and Noah's engagement party, Noah kisses Avery, and she places her hand on his cheek. The camera cuts to another angle, and Avery's hand is by her side.
When Noah and Carrie are getting coffee, Noah's glass level goes up and down repeatedly and sometimes the whipped cream is completely gone only to return again.
When Noah is throwing up in the bathroom, Avery and Ethan change their positioning depending on whether they are seen from the front or back.
The amount of champagne in Noah's glass when he is sitting at the piano at his engagement party changes as the camera cuts to different angles.
When Noah asks the cashier for a blueberry Red Bull, the cashier tells him that Red Bull doesn't make blueberry Red Bull but by October 2014, Blueberry Red Bull had been available for a year and a half.
During one of the 2014 Halloween Party scenes, you can see a girl dressed up as Harley Quinn, in the 2016 Suicide Squad film version of the character. Margot Robbie's first official portrayal of Harley Quinn was not out until May 2015 with an image of the cast, and the first trailer was July of the same year.
Every time Noah wakes up at 6:45, it is very bright outside, but in October and November, sunrise in New Orleans is around 7:15.
If Noah was good enough to play piano at an upscale bar in 10/31/2014, he would not have completely forgotten how to play the piano by his engagement party in 11/01/2017.
Noah and Avery get back to Avery's place still wet from falling in the pool at the party, but some of the lower parts of Avery's outfit are dry.
Successful Noah can't figure out how to decline an incoming call when he is in his car, but he can speak Mandarin and knows everyone's name at the office.
The second time Noah uses the photo booth, the camera took eight pictures instead of four.
When Noah wakes up and. texts Avery, her number was saved in his phone, but they had not met yet. If the number was not in his phone and he actually had to type it in to send her a text, he'd realize something was up since they were close enough friends for him to be at her engagement party.