A Piece of the Action - S2-E17
Continuity mistake: In the very first scene after the intro, when Bela's goons hold the landing party at gunpoint, Spock's position on the sidewalk shifts back and forth from standing on the other side of a wooden bench to standing alongside Kirk and McCoy with no bench in between. In fact, in the latter shots, the bench has moved all the way across the street. (00:04:50)
A Piece of the Action - S2-E17
Continuity mistake: At the end of act one, the cue stick standing upright against the pool table just in front of Spock disappears when the view cuts to an overhead shot. It's back again after the commercial break. (00:11:00)
A Piece of the Action - S2-E17
Continuity mistake: While Kirk and McCoy attack the other two henchmen, Spock shoulder-pinches the card-playing gangster. In the very next shot, Spock's position has jumped from behind the now-unconscious man to several feet away, where he is bending over to retrieve the guns from the floor. (00:16:30)
A Piece of the Action - S2-E17
Continuity mistake: Though the name is spelled "Oxmyx" in the script and pronounced as such in the episode, a poster in Krako's office spells his rival's name as "Okmyx." (00:18:50)
A Piece of the Action - S2-E17
Continuity mistake: When Kirk is talking to Oxmyx across the pool table, the yellow 1 ball is shown close to Kirk, then Oxmyx, and back.
A Piece of the Action - S2-E17
Continuity mistake: The pistol Kirk is pointing at the gangster changes elevation and angle as the scene cuts between the front of Kirk and over his shoulder.
A Piece of the Action - S2-E17
Continuity mistake: The scene outside shows a guard standing close to a sign on the wall that says, "Jo Jo Krako", but the next overhead shot shows the guard further away, and a railing between the sign and the guard that would have prevented anyone from getting close to it.
A Piece of the Action - S2-E17
Continuity mistake: When Krako's men are in the gun battle with Bela's men, the Enterprise stuns them with its phasers. The number of bodies and their positions change after the men are stunned.
A Piece of the Action - S2-E17
Continuity mistake: After Kirk proposes a deal at the end, Oxmyx agrees and points towards the others behind him with his left hand. A second later, he's facing toward the camera with his right hand pointing.
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.