At 5:56, the chair behind Kirk is unoccupied and at Spock's chair sits a crewman in a red shirt. The empty chair behind Kirk appears again at 6:15.
The standard overhead shot shows the bridge fully occupied, but at 2:58, 3:47, 5:00, 6:25 and 16:43 a seat appears empty behind Spock.
No insignias appears on Kirk, Scott, McCoy or Walking Bear when Kukulkan puts them in the menagerie setting at 13:28.
When the Enterprise is under attack at 3:06 (and again at 4:23), Uhura suddenly appears white-skinned in a wide shot. In the same shot, we see a lieutenant's stripes on Ensign Walking Bear's sleeves.
Kirk calls to Scott from the top of the pyramid, but his voice sounds as if he's in a cave, not in the open air. When Kukulkan finally appears, his voice sounds very much as if it is in a cavern, more so than Kirk's did.
Outside of a group shot at 13:28, no insignia on McCoy at 13:33, 18:14, 19:25 or 20:26. Elsewhere there is.
At 6:33, Ensign Walking Bear has left his post at the helm to stand next to Kirk. Kirk has neither invited nor ordered him to do so.
Captain Kirk continuously mispronounces the name "Kukulkan" as "Kuklakan."
At 5:39, Native American Walking Bear has noticeably lighter skin that Kirk, so close to white as to seem drained of blood.
Spock telling Uhura to get back to work is a bit cold and unnecessary, even for a Vulcan.