871,

Even new batteries can have a bad cell and the LED things are only showing voltage. While they give you voltage they cannot test the battery and will not show a bad cell. A loads batteris for several seconds to a couple of minutes will show a battery problem and that is something I recommend you do several times during a flying session (AKA flying many times during on day).

It defintely sounds like you have had a receiver dropout.

Also verify no servos are binding in any way. A servo bonding up will put a load opn the battery and if it's bad enough or you have more than one, you can get below minimum receiver voltage fairly quickly.

While Spektrum is a good system, there are certain things you should be aware of and that is insuring your flight battery setup is in good shape

I use a Spektrum module on my 10X and have also had a DX7. I use Li-ION batteries and still check loaded voltage every flight or even every other flight