Did a broken random number generator in Cuba help expose a Russian espionage network?

I remember concluding that the most likely, if still rather improbable, explanation was that the 9-less messages were dummy fill traffic and that the random number generator used to create the messages had a bug or developed a defect that prevented 9s from being included. This would be, to say the least, a very serious error, since it would allow a listener to easily distinguish fill traffic from real traffic, completely negating the benefit of having fill traffic in the first place. It would open the door to exactly the kind of traffic analysis that the system was carefully engineered to thwart. The 9-less messages went on for almost ten years. (If I were reporting this as an Internet vulnerability, I would dub it the “Nein Nines” attack; please forgive the linguistic muddle). But I was resigned to the likelihood that I would never know for sure.