Equipment Visible: When the Doctor and Todd are talking at the end of the episode, the cut-off tops of some trees can be seen.
The original cut of this episode ran short, requiring the shooting of additional "padding" scenes months later, in the form of the Adric-Tegan scene after Hindle opens the box and some extra shots when the Mara is being attacked. This is noticeable in some discontinuities in the dome set, actors' hair, Tegan's earrings and the coloration on the mirror edges.
Plot Hole: It is never explained what happened to the other vanished members of the expedition.
Revealing Mistakes: When the Kinda surround Aris with mirrors, there is an obvious gap at the lower left for the camera to dolly in and out.