The problem are the sniper standing on the rooftop, not of Jodie, Conan or Akai. When in doubt, anyone worth their salt would have checked for signs of ambushes anyway, and two people standing on the rooftop of the next building is suspicious as hell. Particularly when they clearly have riffles in their hands. Use a window, mate. Or at least lie against the roof.
> We were using our own specialized tools to decode it
Hahahaha, that's stupid. At least don't say that they use computers to decode it.
> They kept on insisting that there was no way that the code has been cracked.
The roman empire 2000 years ago used better crypto. Similar ciphers, but at least they had a key. The AI of the 70's could crack this kind of things automatically by simple statistical correlation, without knowing what a mirror is. Particularly if they are provided probable words it contain, like times or places.