Continuity mistake: When Thunderbird 2 leaves the hangar on Tracy Island, it appears that Pod 3 has been selected (Pod 2 is visible to the right of Thunderbird 2), yet when Virgil and Brains arrive at Mount Arkan, the Transmitter Truck emerges from Pod 6. (The same continuity error also occurs in the episodes 'Vault Of Death', 'Move - And You're Dead', 'Martian Invasion', 'The Perils Of Penelope' and 'Day Of Disaster', probably due to the same footage being re-used for those episodes).
Continuity mistake: When Virgil radios to Jeff that he is about to land on Mount Arkon, Jeff asks him what the weather's like, to which Virgil replies: "Pretty stormy, Father. Pretty stormy." Then we cut to an exterior of the airborne Thunderbird 2, which is absolutely covered in snow. Just moments later we get a long shot and suddenly Thunderbird 2 is no longer covered in snow. We then get a close-up of the cockpit view, where we see Virgil and Brains, and Thunderbird 2 is covered in snow again. We soon get another couple of shots where it alternates between Thunderbird 2 not snow-covered and then being covered in snow again. (00:28:00)
Continuity mistake: When Alan, Tin-Tin and Scott are lowered while on the settee to enter Thunderbird 3, looking head-on at them we have the three of them sat in that order from left to right as they descend the shaft. However, when it cuts to the long shot, Alan and Scott have magically swapped places. When they are fully raised into Thunderbird 3, Alan and Scott are back in their original positions on the settee. (00:18:50)