I like his final speculation, that makes sense.

Repeating the message three times - the flight radio officer knew that he had to send it correctly and he did.  But maybe because it should have been a common group, a new ICAO identifier, he sent it sloppily.  , ETA SANTIAGO 1745 STCI + by rearranging STEND to STCI and EC to + (AR).

That's darned poor sending if he did that and FRO's were top notch operators even if they did remove the weights from their bugs and sent super fast dots and slow dashes as they were known to do - and in South America that was a practice that persisted into the early 21st century.

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