Plot hole: The Doctor and Romana comment on a recording which has finished playing BEFORE they have entered the room. Not only that, but all the other characters behave as if The Doctor and Romana had seen this recording.

Revealing: In episode 1,watch out for the wires pulling K-9 along the beach. (Unlike a real dog, K-9 didn't take well to the soft sandy surface and sank into the sand. Pulling K-9 along on wires provided an illusion of movement when the motor inside wasn't up to the job...).

Other: Romana gives the TARDIS's weight as five million kilograms in the planet's gravity. This is totally inconsistent with the TARDIS's weight in the rest of the series - for instance, in the third Doctor's time, a few soldiers were enough to lift it. And it can't be because of the planet having high gravity, as the Doctor and Romana would have been killed and K-9 crushed whenever they went outside the TARDIS.

Revealing: The Grove is one of the most obvious indoor sets masquerading as a lush outdoor environment. The sound the actors feet make on the floor is especially unforgivable.