ORIGINAL: Allfat
ORIGINAL: 2slow2matter
It's not the trainer switch, it's the binding button on the back.
I've never heard of a radio and rx losing their bind in flight.
On Spektrum radios, the trainer switch is the bind switch. If you hold down the trainer switch and turn the transmitter on, then it will lose binding and you will have to bind it again.
What?
That's wrong. The trainer switch is at the top left (by default) and is a sliding switch (rocker-type). The bind button is on the back, and is a button that is right in the middle of the radio. I own a DX7.