Continuity: The landing party is out of contact with the Enterprise for two days because of the missing communicators. Wouldn't the Enterprise notice at some point and beam down some more, or make some other attempt to contact Kirk & Co.?

Continuity: The dust smudging both Spock's uniform and that of the older security guard instantly vanishes when they walk out of the building to go look for the onlies.

Continuity: The ropes tying Yeoman Rand to the chair keep changing positions (above her elbows or below her elbows) between shots.

Factual error: If Miri's planet is a "duplicate" (meaning identical) Earth, it should have clouds. It doesn't. This remains a mistake because "duplicate" means "exactly the same," and thus the clouds should be there. The special effects crew forgot to put them in. Noteworthy: the very first thing fixed in the digitally enhanced version of this episode was the duplicate Earth. It has clouds now.