Out of the Unknown (1965)
0 factual errors in season 2
Starring: Geoffrey Palmer, Charles 'Bud' Tingwell, Erik Chitty, Peter Copley
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Sucker Bait - S1-E7
Factual error: It is quite true that atoms that do not occur naturally are bad for humans. However, in a space age as this story's, that would apply to most or even all planets. It would be a well known risk that didn't require an abnormal specialist to diagnose. (This fact rarely figures in other SF, because it would severely limit most stories).