During the second Romulan attack near the end, the stars are missing from the lower right 2/3 of the view. Only the top left 1/3 has even a sparse population of starfields.
Near the end, the turbolift doors behind Kirk on the bridge are closed, then open, then closed.
While Bem's ability to split up into individual pieces is noted, it's never explained how they can fly, as they do several times in the episode.
At the 18:15 mark, as Scotty says "Beg pardon, sir?" his hair turns gray.
Why didn't Kirk and Spock just lift up the cage that they are captured in, there is no bottom and it seems to be made out of a light bamboo.
When Spock first collapses on the Bridge, McCoy is suddenly standing next to Kirk--making Kirk's call to Sickbay redundant.
When McCoy briefs Kirk on Spock's illness in the briefing room, there's a brief shot of McCoy from the shoulders up and a tricorder strap can be seen on his left shoulder, although he's not carrying one in previous or subsequent shots.
In one scene on the bridge, McCoy calls Captain Kirk from sickbay for Spock to get another injection. When Kirk orders Spock to go in the next shot, McCoy is standing next to him at the captain's chair. Then when Spock walks by Kirk, McCoy has disappeared.
Just before McCoy shows Captain Kirk the analysis of Spock's blood, the insignia on his uniform is missing.
The door to the conference room should have automatically opened when Spock approached it. He wouldn't have had to knock on it.
There is no sound effect when Mccoy injects Spock with the sythesized drug early in the episode. Also, Spock implies the shot would hurt, but the hypos are designed to be painless.
At the end of the episode Captain Kirk says the Orion ship is in tow, but it's nowhere to be seen on the external shot.
The word "Orion" is mispronounced throughout the entire episode. The cast pronouces it OR'-EE-ON. Kirk cites the Babel conference as having been their last dealings with the Orions ("Journey to Babel"). In that original series episode, Orion was pronounced correctly. OR-I'-ON.
When the Orion captain is beamed aboard the Enterprise and the Orion first officer exclaims that they are gone, his voice speeds up to about halfway between normal speed and Alvin and the Chipmunks speed.
The Orions in this episode are blue-skinned, for reasons that are never explained. Typically Orions are green-skinned, but we've only seen females up to this episode so it would be difficult to tell. It's also possible there are several "colonies" of Orions, and only one is green-skinned.
The perspective was very poor in the temple. When they get inside, we see the sculptured indurite floating, and Sord says, "Pretty bauble. How do we reach it?" From the angles, it looks as if all they have to do is walk across the floor and take it. Even when they scramble up on the ledge, it does not look very far off the ground, but Kirk suddenly makes the comment that it is "a thousand feet up."
The volcano sequence doesn't make much sense. The vehicle grinds to a halt and the lava is flowing just behind them. Then they go to divert the lava, which is apparently now several minutes behind them. Then after they get going the lava is again a few feet behind them, but Spock falls out and Kirk goes to get him and the lava is nowhere to be seen.
Kirk and Spock don't wear force field belts (see entry under Notes for "Beyond the Farthest Star") on the asteroid; but when inside the temple and Kirk walks to the wall, he suddenly has one on for a few moments.
So, was Tchar on the other three teams before, or what? Presumably there were other war-desiring Skorr that accompanied those teams and arranged for their destruction as well at the cost of their own lives, but this isn't very clear and Tchar appears to be a very important Skorr - why wasn't he on one of the other missions?
When was the summoning device mentioned? We apparently hear all of the briefing that the Vedala give Kirk and his team. But in the fortress Kirk suddenly says, "Hit the activation signal" even though it hasn't been mentioned before.