Continuity mistake: When Kirk and Sulu are talking about the details of the peace conference, you can see Sulu on the small display behind Kirk. When Kirk asks when the conference starts, you can see on the small display that someone leans in to tell Sulu the information. When the camera cuts to Sulu the person is no longer leaning in but is standing behind Sulu. (01:28:20)smd9
Continuity mistake: In the opening scene when Sulu is on the bridge and the energy wave begins vibrating the Excelsior, when Sulu's tea cup begins vibrating across the table, it's first seen closer to Sulu. The next close shot shows it vibrating right to the edge of the table. Yet in the next wide shot, it's back where it was near Sulu again. Then in the following close, it's back at the edge, this time sliding off to the floor. (00:04:00)
Continuity mistake: When the Excelsior enters the battle in orbit of Khitomer, General Chang's Bird Of Prey is on top of her. However, when he orders to fire upon her, she is hit from below.