When the crew shoot the iguana, it falls from the rock. In the next shot it's back on the rock, in flames.
The trees and scenery changes as Cosmos III crashes.
Amount of stars inconsistent from exterior/interior shots of spaceship.
After Tang is shot in the right arm, there is no visible wound.
Many of the insignia of rank are either wrong or nonexistent.
Tang's frozen parents clearly move in the ice, despite trying to stay still.
Rocks and stones squash underfoot and wobble.
When the ship is supposedly moving, the stars outside the window aren't moving.
Uniform shoulder boards appear to be those of officers of the Navy Medical Corps.
When the Chief is slapped by his commander.
Shadow visible over door as Admiral King leaves the communications room.
When one of their crewmen is burned in the acid lake and dies, the remaining officers seem unconcerned. While the body might have been dissolved, at least they could feel something for their fellow crew member.