That's been posted a bunch of times - many in this thread...
I don't think that the problems that are reported with the Spektrum system are due to the issue with two closely spaced frequencies. After all, as I said above, that would cause the aircraft to go into failsafe (or at least hold), and what people are saying is the the aircraft not only doesn't respond to their commands, it does other things (what we called a "glitch" in the PPM days...) or at least doesn't go into failsafe (i.e., no idle throttle or turbine shutdown). Other times, the aircraft becomes "unbound" in the air, or on the ground (this failure mode I've seen repeatedly myself). This isn't an interference issue. I suspect a hardware or firmware problem in the RX's...
Bob