While Gordon searches for the Fireflash on the sea bed, the parting in his hair keeps changing sides.
When Gordon returns to Thunderbird 4 after making contact with the trapped crew, the configuration of the puppet-sized Thunderbird 4 doesn't match the model seen in long-shot.
As Thunderbird 4 extends its laser to star cutting off the Fireflash engines the laser is straight however in the closeups the laser torch is angled, and when TB4 turns to cut off the second engine you can see the score line where the engine will break off.
In Operation Crash-Dive (1965), Gordan is seen walking around were all Fireflash's electrical equipment is found, however in the first episode featuring Fireflash's first appearance Trapped in the Sky (1965) when a man is sent inside Fireflash to try and disarm a bomb, he has to hang on to poles and cables. This is because it is either a different area's of Fireflash were used, or the aircraft had been modified after the first sabotage attempt.