Continuity mistake: When Doctor Strange attempts to use the Time Stone on Ebony Maw, Maw ties up Doctor Strange telepathically and strangles him unconscious. Beside Doctor Strange is a police car and a motorbike tipped on its side. Maw then lifts the ground Doctor Strange is lying on, but the police car has been replaced by an SUV and the motorbike has disappeared. The shadows also change. (00:23:25)
Revealing mistake: Just after Proxima Midnight and Corvus Glaive land in the train station, there is a wide shot where they begin approaching Wanda and Vision. In the wide shot, their shadows do not appear to match up with each other, despite being under the same lighting. Proxima Midnight's shadow is positioned in front of her and is quite heavy, but Corvus Glaive's shadow is positioned more to his left and is much lighter than Proxima's. (00:40:20)
Continuity mistake: When Peter sees the ship whilst he is on the school bus, he taps Ned on the shoulder and asks him to make a distraction. When he taps Ned on the shoulder, Ned has earphones in both ears, and one of the earphones falls out when Peter taps him, whilst the other earphone remains in his ear. But in the next shot, neither of his ears has an earphone in them. (00:18:25)
Continuity mistake: Thor says "You talk too much" whilst Thanos has his hand grabbing Thor's head. Thanos' fingers are close together on one side, with his thumb holding the other side. Two shots after, when Thanos asks Loki for the Tesseract, Thanos' fingers are spread apart. Two shots after that, when Thanos says "Or your brother's head", his fingers are suddenly close together again. (00:02:55)
Continuity mistake: When Thor, Rocket and Groot begin charging towards the army after arriving in Wakanda, the shot from behind them shows Rocket and Groot running slightly behind Thor. Then it cuts directly to a shot in front of them, just before Thor jumps into the air, and Rocket and Groot are now further back. (01:45:50)
Trivia: Directors Joe and Anthony Russo like to put in nods to their previous works in their MCU films. In this movie, a man closely resembling Tobias Funke in his "Blue Man Group" makeup (from the series "Arrested Development") is briefly visible inside of one of the Collector's cages behind Gamora for a brief instant. It's hard to spot, but he's there.
Continuity mistake: Whilst they are discussing the plan on Titan, just after Star-Lord tells Tony to not call them plucky, the shot cuts to Tony turning his head to Star-Lord. In this shot, Tony and Star-Lord are positioned around 90° rotated from each other, but in the next shot, the two are suddenly facing each other directly. (01:22:55)
Continuity mistake: When Black Widow stabs Corvus Glaive, she kicks him to the ground and he drops his weapon, with the weapon landing beside him. Proxima Midnight then runs up to Black Widow and Captain America picks up Corvus Glaive's weapon, but it is now much further away from him. (00:41:05)