Continuity mistake: When Pierce's wife is walking in her auto shop they pan down to show her red Louboutin heels, then they cut to her walking in her office, and when they show her shoes again they have a tan sole.
Visible crew/equipment: When the Protagonist passes through Sator's turnstile to return to the ambush site on the highway and gets in the inverted car, a cameraman holding the camera is reflected on the wing mirror. (01:31:38)
Continuity mistake: When driving the silver Audi A6 the first time, the version they are driving is a diesel, seen by the exhaust pipes facing down towards the ground with a bend. In the next shot they are driving the petrol version of the same A6, seen by the exhaust pipes holes facing directly out from the car. (01:18:33)
Continuity mistake: The commanding officer (Donnie Yen) intervenes to stop the sword-pointing nonsense with his kung-fu badassery. He easily disarms the two litigious rookies and holds both their swords, but the pose he strikes is a different one in the two shots; Mulan's family heirloom is held alternatively low and high. (00:29:55)
Character mistake: There are signs out front as the Spenglers arrive at the dirt farm. One of the signs is a call back to a scene in Ghostbusters 1984. In the scene, Ray quotes the book of Revelation: "And I looked, and he opened the sixth seal, and lo, there was a great earthquake. And the sun turned black as sack cloth, and the moon turned blood." When Finn Wolfhard reads it he misquotes the line saying "The sun became as black as cloth."