Hard Times - S1-E3
Corrected entry: In the scene in the church, set during World War 2, Aziraphale tells the two German spies that, upon their arrest, they will spend "the rest of the war behind bars." As a millennia old angel surely Aziraphale must be aware that, without exception, Nazi spies arrested in the UK during World War 2 were shot?
Hard Times - S1-E3
Corrected entry: Aziraphale cites the only prophecy from Agnes Nutter that he could find as one for 1972, "do not buy Betamax" (a reference to the home video format war). Betamax was only launched in 1975 starting in Japan, so this advice should have been for then, not 1972. These prophecies were completely, even ludicrously accurate, so that excludes any explanation that she was simply a few years off, because she was never wrong. (00:19:10)
Correction: Aziraphale is not quoting from The Book, but an extract from a publisher's catalogue, and as a (newly) published author, I can tell you they are rotten with misquotes and other inaccurate information.
It's probably true in your case, but this was a few hundred years earlier? And she would have corrected the proofs, surely? Besides, I don't think the makers deliberately planned this (adding a misprint for more realism).
Correction: Nothing wrong with warning people in advance.
That's what prophecies are for, you say? True, for all of them. But if they come with a specific year and are infallible, then this one is a mistake.
Correction: Not unless he was psychic. During World War 2 the news media was rigidly censored and no reports of the arrest, courts martial and execution of German spies were published. Obviously Aziraphale knows there are German spies in England - he is talking to three of them - but he does not necessarily know what will happen to them if they are arrested.
As well as that, many spies were hanged, not shot. Obviously Aziraphale doesn't know that, either.
And anyway, Aziraphale has shown himself to be remarkably naive and even purposely ignorant at times. I think he would intentionally choose to believe that they are simply going to prison.