RE: Unexplained loss of control
What you looking at is the way the radio transfers signals between tx and rx. After the rx decodes the signal, interference can feed through a servo or battery wire into the receiver if the source is near it.
This happens after the signal is being decoded into a standard analog servo signal, just like the old 72 MHz systems.
Newer receivers do have better filters, but still - noise can happen.
In this case it looks like the power was completely lost. Interference normally causes some servo jitter, seldom total loss of control.
Now a lot of things are involved, something like a locked servo may have drained the voltage, but it could be any part of the electrical system.