Compromised cockpit remains an open possibility.
So do a few other not so happy scenarios.
The transponder thing was true in my fledgling days, but I doubt that 777 has such archaic avionics.
It is amazing how quickly the mods are ditching posts. Wow.
jet noseover:
Yes. Was trouble shooting mine. Turned it off, recycled the CB, turned it back on to stby to warm it up. A few minutes later, with the code assigned, it seemed to work based on ATC getting a good squawk out of me. This was over 20 years ago.