Communication difficulties have often been at the root of many a weak moment in the history of television, let alone Doctor Who. Such a problem occurred in Terminus where the company making the costumes for the Vanir didn't know that the armour created for the inhabitants of Terminus were required for action scenes. They were designed only for decorative use, and so lightweight, brittle material was used in their construction.
The result is my main abiding memory of Terminus - the constant sounds of rattling plastic that occur whenever the Vanir are on camera. Those sounds really begin to grate on the nerves after a while. It reminds me of another sound that just drives me up the wall, that of a room full of people tying on computer keyboards. Thus, any scenes with the Vanir are immediately met with cringing from me. The performances from the actors playing the various members of the Vanir are rather good, particularly Peter Benson as Bor, but their dialogue is constantly being drowned out by either clanking armour or the extremely silly helmets they have to wear that the strengths of those performances are considerably muted.
We also get a better look at the Garm in this episode, which is probably the most derided aspect of Terminus. He's meant to be massive and threatening, but he really is just adorable. I mean, he's a giant walking puppy! Who wouldn't want to just take him home and give him a biscuit? More to the point, why is the only person who seems to be able to help the Lazars a giant, anthropomorphic dog? Does he really come out and take one Lazar at a time into the radiation zone to be cured?
And, speaking of the radiation zone, it is treated with great inconsistency throughout the story. Early on, the Vanir never cross the line between safe and danger zones, even with their armour. Later on, they cross it quickly while wearing the armour. In Episode Three, Valgard enters the zone after throwing away his helmet. Bor has been in the zone for some time with the only ill effects coming from practically lying on the radiation source, couple with being burned by power cables. And finally, The Doctor and Kari wander into the zone with absolutely nothing happening to them, despite the dramatic camera angle used to indicate that they're supposedly in danger. Argh!