Continuity mistake: First, Scotty rigged a self destruct delay timer for Kirk that supposedly had thirty seconds programmed in. However, putting a timer against the one used in the episode, from start to finish there was one minute twenty seconds before the Constellation blew up. Second, Kirk was holding the communicator out and away from himself before his beaming, then it's close to his face as he materializes.
Continuity mistake: Decker is leaning over the forward console between Sulu and the other man, with Spock at his left elbow. As he gives the order to veer off, he starts to turn to his right. As the angle changes, it appears that he was standing straight up the whole time.
Add timeMovie Nut
Revealing mistake: While Kirk watches, the machine fires at the Enterprise. As Spock is knocked backwards, watch his hands as he goes forward. They automatically go into a certain, almost practiced position. Then a moment later, the Communications officer is reporting to Spock. As she does, another shot hits the ship. She and just about all the crew react to the jolt a second before the camera and lighting crews simulate the hit.