Debuting in 1959, The Twilight Zone thrived in large part because of recirculation. The science fiction / horror anthology series spent decades in syndication, winning over new generations of fans with each viewing. However, not every episode in its five-year run reappeared after its original airing. A handful were pulled from circulation for different reasons and remained unavailable for long periods of time. This included one banned Twilight Zone episode titled "The Encounter", which didn't return to television for more than 50 years.
Source：https://www.cbr.com/why-the-twilight-zone-episode-banned-the-encounter/
