The Girl Who Was Death - S1-E15
Audio problem: For some reason, "Londonderry Air" was dubbed over the original song being performed by the actors/singers. Their lips aren't moving in sync with the words at all.
Gold Is Where You Leave It - S1-E19
Audio problem: After the Apaches rescue Blue, Buck signs to their leader and says, "Vaya con Dios to you too, brother." But his lips never move.
Audio problem: After Colonel White thanks Captain Scarlet and Captain Blue at the start of the episodes, they reply with each other's voices.
The Prophet - S2-E11
Audio problem: When the cult brother reverses his car to run over David Vincent, it makes the tires-screeching-on-asphalt sound, even though the vehicle is on a patch of soil, not concrete or asphalt.