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)
Factual error: The location in DC has latitude and longitude both as N/S - longitude is an east/west factor. (00:13:05)
Continuity mistake: After cutting through Black Manta's gun, Aquaman then slams Manta in the face with his trident and knocks him down. As he is twirling his trident in victory, you can see his belt and its design. But then it cuts to a close up of Aquaman and suddenly his belt changes in design with the bar in the middle disappearing and the black of his pants extending further up onto his orange shirt in the belt area. (00:03:50)
Continuity mistake: When April's lying on the gurney, just as she's wheeled through the doorway it cuts to the closeup as the nurse turns to block Fin from entering the ER, and behind the nurse we see the gurney still being turned and wheeled into the room, but April has vanished.
Factual error: The Mountain Dew logo seen in the stadium didn't come out until 1980, despite the film being set in 1973. The changes made in 1980 were subtle, but still distinct, especially the loss of the "wave" in the "D" and the smaller hole on the "a."
Continuity mistake: When Cooper draws on the board and talks about landing on water, his drawing changes between shots. (01:04:25)
Factual error: The solar panels (or mirrors) are facing away from the sun. The sun's position can be estimated from ground shadows and object highlights and the panels are facing in completely the wrong direction. (01:11:40)
Continuity mistake: When Quill and Gamora first meet and get into a fight, Gamora grabs the Orb Quill is carrying and runs. Quill throws a sort of laser-based "lasso device" that snares her legs and causes her to fall. She pulls it off, and immediately in the next shot, it's vanished from the ground between cuts. It also had mechanical components, so even if the laser vanished, the mechanical pieces should still be on the ground.
Continuity mistake: During the gunfight in the arms dealer's hideout, Robocop enters brandishing his futuristic 'M2 Battle Rifle' which then immediately changes to an MP7 in the next shot. This error gets particularly blatant during the following shots from his POV, where he's shown still firing the M2 in his HUD, only for the scene to immediately cut to show him firing the MP7.