And the Children Shall Lead - S3-E4
Audio problem: When Spock asks Kirk, "Why are they bothering Starfleet?", there is a loud buzzing noise twice as they are focused on Kirk's face.
Continuity mistake: When Scotty thwarts Garth, disguised as Kirk, attempts to beam to the Enterprise using the Queen-to-Queen level three code, Kirk throws a tantrum and accidentally loosens one of his controls during his rant right before he turns back to Garth.
Suggested correction: How is that a mistake?
Continuity mistake: After Spock nerve pinches Chekov when he goes mad and he is taken to Sickbay, the Tholian ship appears and hails the Enterprise. When Spock says "on main viewer," the shot of Loskene is on the screen, but the back of Chekov's head can be seen when it should be in Sickbay.
Is There in Truth No Beauty? - S3-E5
Visible crew/equipment: Spock and Dr. Jones carry Koldos into his quarters, and when Spock walks over to the wall communicator to contact the bridge, the camera casts a shadow on the wall as it moves closer to Spock. (00:05:20)
Is There in Truth No Beauty? - S3-E5
Visible crew/equipment: At the dinner, when Miranda stands up to leave, there's a visible white tape mark on the floor near her feet. Then, when McCoy makes his exit Kirk reaches for the rose, and there's a better view of the white tape mark under the table. (00:11:50 - 00:13:45)
Audio problem: Spock uses the intercom to call Mr. Scott who is in engineering. As the shot cuts to a side view of Scotty standing at the controls, he answers "Scott here" but his mouth or lips never move. (00:44:24)
Continuity mistake: In the turbolift, Chekov is standing to the left, but when the door opens he has moved to the right and exits behind Spock. (00:10:40)
Continuity mistake: When Scotty, Kirk, and the others follow Spock's signal to the chamber with the Controller, they encounter Kara and she activates their pain bands. Spock's body has a pain band around his waist as the other men drop to the ground, but after McCoy tells Kirk, "Spock, no pain," the pain band is missing from Spock's body, then in the next shot it reappears when he goes after Kara's bracelet. (00:35:05)
Continuity mistake: When Kirk and his landing party beam down to the planet there are six shots of Morg, who have their right arms covered in fur in all those flipped shots, but when Morg attack the landing party it's their left arms covered in fur. Presumably, the first six shots were flipped for direction continuity. (00:13:15)
Continuity mistake: When Kirk and Mara are in the transporter room for intraship beaming, Kirk is wearing his usual Starfleet boots with heels, but while Kirk and Kang are fighting Kirk is wearing flat bottom boots. (00:43:25)
Let That Be Your Last Battlefield - S3-E15
Other mistake: At the end of the episode, as Lokai is running through the ship, his hands are empty. However, in one closeup shot he is holding onto a rope with his left hand. The rope is gone in the following shot. Presumably this rope was used to tether him to the camera as he ran so that he could maintain distance from the camera.
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.
Revealing mistake: When Abraham Lincoln shoves the Klingon away from him during their fight, the Klingon collides with a heavy boulder which moves several inches at impact.
Other mistake: As Kirk and party duel against the Klingons, there's a heavy-looking round conduit on the wall right before the turbolift door that gets knocked down so it stands as a big flower pot. A moment later, it's back in position.
Continuity mistake: The first time we see the ship travelling at Warp Nine, it is moving in a level, straight path. Next time, the rear end is elevated above the line of flight. The next time, it's moving in level flight again.
Audio problem: The bartender comes over and brings whiskey and five glasses, but we hear six glasses hit the table.
The Empath - S3-E12
Revealing mistake: When the Vian fires his weapon at Kirk after the crew finds Gem, Kirk flies backwards. At this point, Kirk is not William Shatner but a stunt double.
Continuity mistake: As Kirk wipes a tear from Elaan's face, both cheeks are wet. A second later, both cheeks are dry.
Factual error: Throughout the episode, there is a constant reference to 5 p.m. being the time Kirk and crew (a.k.a., the Clanton gang) were to die. However, the real 30-second shootout was at 3 p.m.
Visible crew/equipment: The shadow of a boom mic is seen against the rock walls of the cave follows Spock and McCoy when Spock pulls McCoy off Zarabeth.