At the press conference before the Japanese Grand Prix, Hunt is smoking with his right hand while simultaneously nervously flicking his lighter with his other right hand.
(at around 1h 28 mins) Just after Lauda's 4th place finish in his first race after the accident, there is a fan sitting atop the billboard, in a purple shirt and waving a flag. To his right, about 6 to 7 feet away, there is another fan in a green shirt, pumping his fist in the air. In the next shot, these same two fans are sitting immediately beside each other, their legs almost touching.
James Hunt pits in the Nurburgring behind Team Tyrrell (Patrick Depailler). However, when he looks at his side mirror he clearly see's Niki Lauda, which would be impossible since the Tyrrell is in between Niki and James.
On the morning of the 1976 Japanese Grand Prix, Hunt gets out of a bed that shows two other sets of feet. This is the same bed, with the same feet as that shown in a montage of fun-loving Hunt later in the film - where the feet are shown to belong to two air stewardesses.
When Niki crashes at Nurburgring, his car is hit by another racer and pushed further down the track. When the replay of the accident is shown on TV with James Hunt watching, the first impact shows Niki being pushed to a different part on the track - over the white line and to the side.
Throughout the film Niki Lauda's nationality is shown in the stats abbreviated as AUS - this would be the international code for Australia. Austria's code is AUT.
The Nürburgring racetrack is referred to as "The Graveyard", while its actual nickname was "The Green Hell".
During the Japanese Grand Prix, Hunt was first overtaken by Patrick Depailler, not Mario Andretti. Despite the commentator saying Hunt needed to finish at least third to win the championship, fourth would have sufficed. The scoreboard error, putting Hunt in 5th, was corrected before the race was finished.
Driver François Cevert was not decapitated in his fatal accident at Watkins Glen but split in half. The incident depicted in the film is an amalgamation of two fatal crashes at the circuit: Francois Cevert in 1973 and Helmuth Koinigg in 1974. Lauda witnessed the Cevert crash but the Frenchman's car was inverted on top of a guardrail. It was Koinigg's car that went under the guardrail, decapitating him. Also, Cevert was driving the #6 car, but the film depicted him in the #9 car.
In the German GP, Nuernburg Ring , Lauda is shown campaigning to get the race stopped, whereas Hunt is insisting that the race go ahead. In fact, Lauda and Hunt (who were actually very good friends) discussed the matter and agreed that it was very dangerous; neither wanted to race. It was other drivers, including Clay Regazzoni and Alan Jones, who pushed for the race to go ahead. In the Japan GP, Hunt fully supported Lauda's early retirement from the race, and always said he wished they could have shared the title.
When Hunt is watching the TV news of Lauda's crash, there is a lot of visible damage on the film, even though it was supposedly just taken. This is because it is the actual footage, not a recreation for the movie.
The newspaper that is handed to Hunt has a repeating paragraph in the right column visible, starting with "Only hours earlier...".
When Niki Lauda and Marlene Knaus have a breakdown, when the first car doesn't stop you can see the skid marks on the road caused by the second car (which did skid to a stop). The car passes were evidently filmed out of sequence.
After Niki Lauda, asks the doctor to vacuum the fluid from his lungs a second time, and opens his mouth, actor Daniel Brühl's real teeth are visible behind the dental appliance veneers.
In the scene in Italy where Niki and Marlene hitch a lift, the subtitles refer to him as 'Lauder' not Lauda.
When Niki Lauda and Marlene Knaus have a breakdown in their first meeting scene, the second car that stops for them is left in reverse and stalled when the driver climbs out of the car (you can see the car abruptly jumping backwards and hear the engine die).
Throughout the film, OMP race suits are shown with the new OMP logo, which wasn't designed until 2012.
When James Hunt is flying and takes notice of the flight attendant, the airline seats shown are Lufthansa First Class seats that were not introduced until 2001.
When James Hunt is introduced to his new Formula 1 car, he is wearing a Franklin & Marshall tennis shirt. In the early 1970's Franklin & Marshall was only a college in Lancaster, Pennsylvania and not yet an Italian fashion line. This shirt would not have existed until 1999.
The McLaren team has a Mark 2 Transit van in their pits at the '76 British GP. The Mark 2 was introduced in '78.
Drivers are wearing modern day racing helmets in some racing scenes.
James Hunt receives a telephone call on his "Trimphone" which had an electronic warble to announce incoming calls, not the ringing bell heard on the soundtrack.
When Lauda is in his car before the start of his first race after his accident, he's seen revving his engine. When the camera looks over his shoulder at the tachometer, as he increases the revs, the needle moves down, instead of up, as it should. This is repeated a couple of times.
When the ambulance go through the pit lane, you can see the rig for the camera attached to the side of it (black tubing).
When Niki Lauda and James Hunt are racing at the Nurburgring, both cars go into the pits to change to dry weather tyres. Before Lauda leaves the pits, Hunt is shown driving around the renowned Carousel corner before Lauda had left the pits. This corner is is around 2 thirds of the way through the circuit, and would be approximately 5 minutes away given the conditions.
When Lauda meets Marlene for the first time, he asks her for a lift to a train station nearby, and she answered that Trento's half an hour's drive. Clearly they are somewhere in central Italy with no mountains in sight, which means hours away from Trento (city in the Alps).
In reality, the Paul Ricard circuit is a flat and the pit straight is a proper straight instead of a kink as featured in the movie. The circuit used for filming the scene of Lauda's testing with BRM was the Brands Hatch circuit which actually hosted the British Grand Prix in 1976.