I presume that "dry tube housings" refers to the side nacelles as we call them. The goof is "When Gordon returns to Thunderbird 4, the camera angle reveals that the side nacelles on the puppet-size model extend backwards only a very short distance, instead of all the way back to the rear of the vessel."

I added that point in the trivia section for Up from the Depths Part 2; this is exactly what I was talking about.

In Operation Crash Dive, there is a scene where Gordon swims back to Thunderbird 4. The model that was used for this close-up shot only consisted of the front of the craft. As such, the rear of the craft isn't visible and, because of the camera angle used when recording, this is shown. This can be seen in the last image on the "goofs" page.

In Up from the Depths Part 2, Thunderbird 4 is snapped at the same place. It could be intentional or just be a coincidence. I thought it was worthy of a mention though.

Ok