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.
Audio problem: When Kirk demands to know who the Troglytes are, his voice is dubbed over: his lips don't move at all. (00:04:05)
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)
Revealing mistake: When Kirk pushes Plasus against a rock wall in the mine, a huge upper section of the "solid rock" wobbles. (00:43:20)
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.