Revolt of the Androids - S2-E24
Revealing mistake: Watch closely the two scenes involving the Robot; (1) When the Omega 17 IDAK battles with the Robot you will see pieces of his plastic collar continually. (2) After Verda and the Alpha IDAK disappear you will notice the Robot's lower shutter falls out.
Revealing mistake: When the family are in the tubes so duplicates can exist, you can see some movement. Dr Smith blinks noticeably.