Revealing mistake: The raindrops on the faces of Eddie Houseman and his colleagues during the storm are disproportionately large.
Suggested correction: This is part of the art style of the show - the same reason everyone's eyes are so disproportionately large, it helps the viewer to see details that would otherwise be too small to spot.
Other mistake: Every time Thunderbird 3 is used during a mission, members of the Tracy family enter it by being lowered on the settee onto a mini rail system, which takes them to Thunderbird 3's hangar before a pole raises the settee into the ship. However, during the initial descent, there is usually an empty settee that passes behind the descending one carrying the impending Thunderbird 3 crew, to fill in the resulting hole in the floor. If the ascending one passes behind the descending one then there is no way that it could fill that hole as it would be too far back.
Suggested correction: As we see the replacement sofa correctly located, the fault is that we do not see the mechanism for doing this. For example, the poles might have been angled to achieve the effect or the start of the rail track might shift over a bit.