Continuity mistake: When Sarah falls from the scaffolding, a plank of wood saves her from death. Trouble is, she fell a foot from the outside of the scaffolding and most of the plank was inside the scaffolding, therefore her feet would have hit it and she could only have landed with her head pointing inwards. But when we see her, her head is pointing outwards.
Continuity mistake: At the very beginning, Sarah comments to the Doctor that they haven't returned to "the beacon". But when they were last on Nerva - in Ark in Space - it was referred to as a space station. It doesn't become Nerva beacon until the next episode.