If you use a better servo than the Eflite one, like an HT 45 or HT 65 with ball bearing shaft and karbonite gears you can have fast response and light weight with lower current draw.
I had not considered brown out, another reason to bench test all the components together.
Look at the spec sheets, 45 is smaller. You want to buy a slightly better version of what was in it to begin with, not something twice the size. I have no idea what the original servos are like in your plane. Those were examples of faster acting, more durable servos without the current draw of a fully digital metal gear 9g.
You have a SAFE receiver right? Unless you turn off AS3X, all those servos can be commanded by the flight controller to be running to stabilize the plane. Aileron (2), elevator (1), rudder (1). Add in flaps in an extended position, and you could have (assuming 2 flaps servos) 6 servos drawing from your poor BEC all at once.
They of course link to a flitetest video that discusses all this (good discussion on digital servos as well):
Yes it has SAFE and it was on. My flaps weren't deployed, I don't like taking off with them but I believe I might have hit the gear retract switch which are probably a heavy draw more than a regular servo.... That might have been when I lost control. I can't remember for certain but I had just taken off and my usual action is to retract the landing gear.
Damn this is all stuff I didn't know, I wish it hadn't been such a costly lesson lol.
Wow that video is excellent at explaining brown out... That's scary I had no idea. I'll have to look at the draw for the metal vs the original ones and see what the difference is. This has been really informative than you everyone.
If the servos checked out and still are OK and the Rx passed its range check you are really only left with a couple of possible issues, (if you exclude some random intermittency), and they are either there was a massive interference, (DoS), event across the entire radio band/channel your radio was using, the ESC/BEC overheated and shutdown the Rx voltage supply, or there was an antenna induced LoS event.