Continuity mistake: When Darcy is at the site in the Arctic, the frozen Dinobots she sees do not appear until she walks up to them. In the establishing shot of the site, they are nowhere in sight. And in the shot where the site worker is pointing a shotgun at her, the only things seen in the background are the vehicles on the site. The frozen Dinobot suddenly appears in the background when she continues to walk towards it. (00:03:05)
Continuity mistake: When Cade and Lucas are walking up to the theatre, in the shot where they are approaching the owner, he is shown leaning against his car and facing away from them. The shot then cuts to the owner, where he is suddenly facing towards them. (00:04:50)
Continuity mistake: When the girls in the red jeep pull up to the mail boxes, Tessa gets out and says "almost time for a tan and get wasted." Another girl then gets out and throws one arm up in the air and cheers. From the front shot, you see that both her sleeves are still over her shoulders, and her hair is over her left arm, which is down. From behind and the sleeve on her left shoulder is down so her arm is showing, and her hair is now behind her back, with her pink bra strap visible. (00:07:10)
Continuity mistake: When Cade is forcing the real estate agent and the two buyers off his lawn, he threatens them with a baseball bat. The bat is in his right hand as the three get back inside the car, but as soon as the car begins to drive out of the lawn, the bat has suddenly switched to his left hand. (00:13:15)
Continuity mistake: When Cade is showing Tessa the photo of him and her mother, the right corner of the frame is shadowed compared to the rest of it. A few seconds later, when Tessa begins to walk away, the shadow in the right corner of the frame has disappeared. (00:23:05)
Continuity mistake: Cade says that this is a no dating household, that he doesn't date and neither does Tessa. Tessa then says that maybe he should, and storms off outside. Cade follows her, and as you see him leaving the shack, there is nothing in his hands. But when he gets outside and catches up to her, suddenly he is holding a power drill in one hand, and an adjustable wrench in the other. (00:23:15)
Continuity mistake: When Tessa and Lucas are telling Cade they need to get the truck out of the barn, Cade says he's been working in there all night, and he is fine. His arms are raised when he says this, but when the shot cuts, his arms are suddenly by his side. (00:26:05)
Continuity mistake: Lucas returns from getting parts for Optimus Prime, saying he went to the doctor. As he pulls up in his car and parks, his window is up. But then it shows him open his door and climbing out, and suddenly the window is halfway rolled down. (00:33:20)
Continuity mistake: When the agents of Cemetery Wind arrive at Cade's house, Lucas is shown in a close up hiding behind a tree, looking out. His arm is stretched out beside him, obviously his hand on the tree and him close to it. But then it cuts to a far shot from behind and suddenly his arm is down and he is further from the tree. (00:34:55)
Visible crew/equipment: When the red car flips through the truck during first car chase after locating Optimus at the house, the first shot doesn't show anything there, then after the car flips through truck, a camera is shown on the ground, presumably filming but looks like they never used the shot. (00:41:53)
Continuity mistake: When the Autobots are reunited it shows Bee, Crosshairs and Drift in his Bugatti form all driving together, than all of a sudden Drift is up on the mountains and jumps off into his helicopter form. (00:52:29 - 00:52:56)
Visible crew/equipment: After Drift transforms into a helicopter, Optimus Prime continues driving through the desert. In the first shot after, a camera truck can be seen reflected in the chrome bumper. (00:53:15)
Factual error: Darcy tells Joshua Joyce about the meteorite that caused the dinosaurs to become extinct; she mentions that the piece of metal in question has been carbon dated to 65,000,000 BC. Carbon dating is limited to around 40,000 years. For longer time periods potassium-argon dating or other techniques are used. Additionally, carbon dating is used for life forms, not for metal. (00:58:45)
Continuity mistake: When Bumblebee acquires his new Camaro look, Tessa and Shane are sitting inside him. After the new look is complete you get a camera shot in front of Bumblebee where you see that no one is inside the car. In the next shot both are sitting back in it. (01:10:00)
Revealing mistake: When Bumblebee drives up the KSI building, he swerves the car around to face the building and let Tessa and Shane out. The tyre marks are visible on the ground before he swerves the car, most likely from a previous take. (01:12:10)
Revealing mistake: When Galvatron is firing rockets on the Autobots, a flatbed truck swerves into the back of an RV causing it to flip over and explode. There is no driver in the RV. (01:17:40)
Continuity mistake: Optimus and the car Tessa is trapped in are caught in a net and are pulled up to Lockdown's ship. Cade then jumps and grabs onto the net whilst it is being raised. There is a brief moment where Optimus is not visible inside the from the net, before being visible again in the next shot. The CG artists likely forgot to add Optimus into the shot during post-production. (01:22:35)
Continuity mistake: When Tessa is on Lockdown's ship, she comes across the Cemetery Wind team making the trade with Lockdown. In the shot shown of Tessa looking at them in the background, the helicopter that Cemetery Wind arrived in has its propeller spinning really fast. It then cuts to Savoy, where the propeller is moving much more slowly and about to stop. (01:27:30)
Continuity mistake: When Lock Down is giving the seed to the CIA the scratch on his chest is top left to bottom right, while in the rest of the movie it is top right to bottom left. (01:27:35)
Continuity mistake: During the scene in which Tessa is hanging onto the wires suspended above the skyscraper, Lockdown's dogs start crawling on the wires behind her. The dogs then disappear in the next closeup of Tessa, only to reappear in the next shot. (01:39:10)
Chosen answer: The battle that lead the government to hunting all transformers was in Chicago, but the incident that took Optimus out of commission was not. He'd been on the run for however long, even changing his appearance to avoid detection, when he was ambushed. Wounded, he snuck into the theater to hide before transforming one last time into vehicle form at which point he basically passed out, lost consciousness, or whatever it is robots call it when they involuntarily shut down (stasis). His aggressive reaction upon waking is simply down to his instinctive warrior reflexes immediately kicking in. All humans are a potential threat to him now, so he reacted accordingly in an instant.
Phixius ★