Doctor Who (1963)

The Invasion - S6-E3

Revealing mistake: The Cyberman that falls from the roof in the final episode is obviously an empty costume. (This is another example of a mistake being repeated from an earlier episode. See the earlier story "The Tomb of the Cybermen" for a note about the same 'revealing' mistake happening).

The Seeds of Death - S6-E5

Revealing mistake: When Jamie is wrestling with one of the Ice Warriors in a storage room, one of them gives the wall an almighty knock and it nearly falls down.

The War Games - S6-E7

Revealing mistake: When the resistance are storming the landing bay, one of them punches at least a foot to the right of a guard's face, but he still collapses.