Factual error: In the scene where the young Helen Goff is traveling by train with her family, it's obvious that an American engine and coaches have been used, instead of a Queensland Rail locomotive of the era. None of the QR locomotives had flared smokestacks like on the one seen in the movie. The coaches are also incorrect - as far as I know, none of the Queensland Rail wood coaches had clerestory roofs with a set of windows in them like seen in the movie. When Helen looks out the back of the train, it's also obvious that the tracks are spaced at 'standard gauge' (4' 8.5"). They should be closer together, as railways in Queensland are built to 3'6" gauge instead. There is also no such company as the 'Queensland Victoria Railway Co', as marked on the coaches, as all railways in Australia are state owned.
Factual error: When Llewyn is driving back to NYC from Chicago, he passes a couple signs stating that Akron, OH, is at the next exit off the highway, on US Route 80. US 80 passes exclusively through the South, from Dallas to the Atlantic Ocean in Georgia, and doesn't even come remotely close to Ohio. (01:13:58)
Suggested correction: It's Interstate 80, which does pass through Ohio, not Route 80.
The mistake is correct. It's the US Route 80 sign which has black letters on the white shield. An I-80 sign would have white letters on a red and blue shield.
Audio problem: When the Police play "Roxanne" for Hilly, the actors are just lip-syncing to the studio version; though his laugh has been edited out, the atonal piano chord at the beginning of the song, a now-famous gaffe from when Sting accidentally sat on a keyboard during recording, still remains.
Visible crew/equipment: When the group are finishing the recording of 'Tell Me if You Wanna Go Home' on the rooftop and Dan and Violet's guitar solos are finishing, the shot begins to pan out. Just before it reverts back to a close up, on the left hand side of the shot a crew member or piece of equipment slips into the shot (the shadow is also visible on the ground).