As you can see the Autolock has appeared on both sides of Thunderbird 4. I am now presuming that two sets were made of Thunderbird 4. From my research, the Airlock has appeared more times on the right side (ect: Desperate Intruder) rather than the left side (Day Of Disaster).
The studio is unlikely to have made two sets, although like other vehicle interiors, Thunderbird 4's cabin would have been upgraded for later episodes. The appearance of the Airlock on different sides is probably more likely to be due to the set only having one side section, and this would be swapped from side to side depending on the camera angle required.