RE: strange crashes
I agree, sounds like a radio system issue. Could be receivers, could be the transmitters.
Also, what kind of batteries are you using? How many cells? what capacity? what are you using to charge them?
I'd take a close look at the switches and all the connectors too.
If everything looks good, I'd call Horizon and send the transmitter and crashed receivers to them. These guys have great service and will likely make it right. The DX-7 is a great radio system but yours may have a problem.