Let That Be Your Last Battlefield - S3-E15
Continuity mistake: The planet Cheron is blue the first two times we see it on the view screen, but when the Enterprise enters orbit, and every time we see it thereafter, the planet has mysteriously turned red. (00:44:05 - 00:46:00)
Continuity mistake: When Kirk beams down to the planet, he selects the front transporter pad next to the steps, and closest to the door. When he materialises in the replica transporter room, he is on the same pad. When the scene cuts to a view of the empty transporter room, Kirk is no longer on the front pad. The scene cuts again, and Kirk steps off the front pad to walk to the control panel. (00:00:30 - 00:01:30)
Continuity mistake: When Kirk splits up the landing party, he asks McCoy to further inspect the vegetation. In the two shot, McCoy isn't wearing his tricorder, but in close-up, it's there, strapped over his left shoulder. Cut back to the two shot, though, and it's gone again. (00:10:20)
Continuity mistake: When Losira appears to D'Amato, he looks up from his tricorder, startled. The shot then changes angles, and D'Amato looks up at her all over again. (00:11:55)
Continuity mistake: When Mr. Scott asks Watkins to check the bypass valve, Watkins is facing the engineering boards with both hands on the panel. When we cut to a different angle, however, he's suddenly jumped to a position facing Scott with only one hand on the panel. (00:18:35)
Continuity mistake: When Losira comes for Kirk, he's holding Sulu's tricorder with both hands. When the angle changes to include her, he has it in one hand with his right hand at his side. Cut back to a three shot of Sulu, Kirk and McCoy, and Kirk has the tricorder in both hands again. (00:36:55)
Continuity mistake: When Kirk intervenes to keep Losira from touching Sulu, she jumps back about two feet and stops. When the camera cuts to look at her, she's still moving, and is about ten feet from Kirk.
Continuity mistake: On Memory Alpha, the viewer beside the dead man in the purple jumpsuit keeps moving from his left side to his right and back again between shots. (00:09:10 - 00:10:10)
Continuity mistake: As Mira is speaking with the alien's voice, Spock is behind a console that has a piece of equipment attached to it. From behind Spock, the piece is to his left, but the close ups of Spock show him close to and directly in front of it.
Requiem for Methuselah - S3-E19
Continuity mistake: When looking at the view screen from the helm, there is a man sitting at the Conn position, but in the wide angle, there's a woman there.
Continuity mistake: The leather strap with which the Troglytes lasso Spock disappears and reappears repeatedly from around his waist and shoulders during the scuffle at the mine entrance. (00:04:30)
Continuity mistake: In "Amok Time" Spock described Vulcan mating rituals as "a thing no out-worlder may know" - here he goes on about them with Droxine at some length.
Continuity mistake: Lincoln asks Kirk if they measure time in minutes and Kirk replies "We can convert it." In every previous episode they've always used minutes - their ship chronometers are still set to minutes.
Continuity mistake: During the hand-to-hand fight scene, the stunt double playing Spock gets his hair mussed up, but immediately after the fight, Spock's hair is neatly combed and formed, as it was before the fight.
Continuity mistake: In Kirk's log entry, which he somehow makes from jail without a tricorder, he states that 5 witnesses heard him speak to the "spirits." This isn't true, and Kirk ought to know it. The crowd rushed in through an archway after he spoke to Spock and McCoy, and they were all too far away before to hear him. (00:10:50 - 00:26:00)
Continuity mistake: When the prosecutor visits the cell, Kirk's hands on the bars change positions when the camera angle reverses. From the inside, there's one bar between Kirk's hands. From outside, there are two. (00:28:10)
Continuity mistake: After Kirk knocks the jailer out, there's a bit of stew on the cell's door above the lock. After Kirk drags the man into the cell and closes the door, the bar above the lock is clean and dry.
Continuity mistake: Lt. Galloway, who was killed off the season before in "The Omega Glory," is resurrected without explanation for this final episode. (00:24:25)
Continuity mistake: During Spock's Court Martial, Chekov says that General Order 4 is the only exception to Starfleet's no-death-penalty policy, and Sulu and the others agree. However, according to "The Menagerie," that exception is General Order 7, not 4.
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.