Wander,
as you will know the morse for E is a single dit and the morse for A is dah dit. The thought was that in fact it should have been read as a single morse letter dit dah dit. Which is R. So the message would be 'STRDEC and not STENDEC. As morse is one of the 'modern' shorthand texting systems this theory (not mine) seems to make as much sense as any other. As a Radio Amateur I have more than once misread a transmission in a similar manner especially when conditions were difficult. We will never know for certain of course.