So, the Hobbyking redbrick is a budget ESC and probably overrated. The BEC is probably weak.
How many servos are on that plane?
Another issue is heat, do some static testing and see if the ESC gets warm only or gets very hot.
As for RX shadowing, it's common if you're using a budget RX with one short antenna.
An RX with dual and lengthy antennas around 20 - 25 cm each would be ideal.
Another simple check is to know your TX battery voltage. I don't use rechargeable AA nimhs, only alkalines. My DX6i has a voltage meter for the batteries.
I've read the same thing about the Redbrick ESC at quite a few places now.
There were only two servos (elevons only configuration).
I will do a round of static tests, but it will probably take me a day or so to be able to run them. Quick question here - since I've kept the battery at storage charge for now, before running the tests should I recharge the battery back to full?
The RX antenna is a single antenna, and is short. I have not messed around with it because I know folding it can change it's electrical length to half. Is it possible to hack in another antenna (or maybe just solder another short wire to it?)?
I use normal Zinc carbon manganese batteries for the transmitter, and the Turnigy 9X showed a voltage of 10.1 at the time of the crash (8 cells, so max voltage is less than 12V with fresh cells).
Good news I think I found your problem.
I have the Redbrick 30 amp esc. I used a watt meter and a Turnigy IR thermoter. At only 3 seconds of full throttle with 12 amps and 165 watts on the watt meter, the ESC temps went to 70C and was too hot to touch and this was the ESC in open air behind the prop. I imagine your ESC is blanketed by foam with no fan on it so I'm sure it's overheating and shutting down completely temporarily until it cools off.
In your static test, test it yourself with a watt meter and an IR thermometer. If you don't the equipment, go full throttle for 10 seconds then touch the ESC. If you can't keep your finger on it for more than a second, it's in danger of burning out. But it's better to use the IR thermometer.
Wow! Terrific of you to try it out - thanks so, so much! I will run a a static test in a day or so and be able to come back with results.
The ESC, while inside the foam case, would have gotten very good ventilation because it is squarely in the middle of the air intakes.
Any specific IR Thermometer that you recommend? For measuring wattage, is a multi-meter good enough or is there a specific watt meter that you would recommend?
Thank you again!!