When reaching what is termed as the large body of water, the characters clearly stand next to water that is only as mildly agitated as a mill pond. Cut to what they are observing, namely, roaring waves crashing brutally on some rock. After this insert, there is a cut back to the characters standing at the edge of the comparatively calm water.
As Professor Robinson, Don, Will and the robot travel in the chariot with the interior temperature rising, the camera shots of Prof. Robinson and Don show them moving away from the terrain, as if the chariot is moving sideways.
The sweat on Will's face & damp hair while riding in the chariot through the desert disappears after arriving in the cave.
At 14 minutes, one of the slats on the robot's lower belly is missing revealing a 3" reel of audio tape and some of the robot's inner workings. Moments later, the slat is back covering the robot's workings.
As the temperature rises to 130 degrees while riding in the chariot through the desert, Will's sweaty damp hair is separated down the middle of his forehead in the interior wide shot. During the next closeup, his damp hair is combed together covering his entire forehead but goes back to divided down the middle in the next interior wide shot.
In order for the subterranean jungle to survive, the plants and trees would need an incredible source of artificial light in all areas of the underground world.
As the robot is revealed to have two inseparable caterpillar tracks for propulsion, it would be impossible for it to negotiate the vast step down to leave the colonists truck vehicle without either using its claw-like hands or toppling face first to crash into the dirt, yet it is clearly seen doing so with a camera shot from the waist up.
It seems remarkable that the floors of this underground cavern complex should at all times be as smooth and flat as a concrete TV studio floor.
In the opening teaser, the Chariot is driven too close to a "boulder", causing it to move as it brushes by.
At about 41 minutes the control panel for the restraining device is seen with buttons and controls for "Memory Address" and other computer related functions, but nothing to do with the restraints. Also, it is unlikely wording would be in English on an alien device.
Despite the jungle being deep in underground caverns, no explanation is made for why the backdrop is of a clear sky as opposed to a rock wall or the source of the ubiquitous light, when everything should be in pitch black.
The princess frees John but refuses to free Don. Though she is distressed when John tries to free Don against her wishes, the guard stationed in the room (who salutes the princess when she enters, and whose legs are seen standing behind her) does not move to aid her in trying to stop John. His order, it would seem, is to be only a room decoration.
All in the same cave together, Will and the robot experience two jarring earthquakes while Don and John do not. (Later John and Don experience their own jarring earthquake in the subterranean world while Will and the robot, in the same world, do not.)
When the princess frees John but leaves Don restrained, a moving shadow on the wall behind Don suggests there's another prisoner restrained in the same standing position as Don, possibly around the corner. Since this is a closed subterranean society in the business of stockpiling soldiers in suspended animation, the owner of that shadow would have to be a member of that society, but John never seeks to aid this prisoner -- nor does this prisoner (or the guard in the room, for that matter) call out about prisoner John escaping. Later when John returns to free Don, the shadow on the back wall of this unknown prisoner is gone.
Given the technology and power available on the Jupitar 2, surely the castaways could distill salt-water if that was all they could find.