I did a maiden of a 210mm quad today. During a short punch-out burst it just stopped and fell to the ground and I'm wondering what the cause could have been. I'm quite new to the hobby and it's not always clear to me how to diagnose situations.

parts:
- 1806 2300kv motors
- KingKong 12A BlHeli Opto ESC's with dampened-light
- 50x40x2 props
- Afroflight Naze32 rev6 flight controller
- LemonRX DSMX compatible receiver
- Turnigy nano-tech 1300mAh 3S 45~90C Lipo

I did the first flight on a 2S lipo and all went nicely. Then I switched to a 3S, did a few easy fly-by and of course got greedy and punched it a bit. The thrust of the punch surprised me so I quickly throttled down, which made the quad begin to topple over as it started falling down. I then pushed the throttle up again but the quad didn't react at all, commencing to crash into the ground. I turned it off the quad at that point and haven't turned it on again before I have some more info.
Doing a sniffing test, I can smell that the rear two ESCs have more of a burned smell than the front two, with one of the rear ESCs being a bit worse than the other. It's unclear to me if this is an indication that they're fried or not. I don't see any black marks on them. What would you advise is a sane and safe way to test them? I'm also curious what and ESC behaves like when it burns out or starts to get overheated. Does this cause the quad to cease all action? Or would it all of a sudden send the quad into a crazy spin? The motors weren't hot, by the way.

Is it possible that the LemonRX receiver had a brown-out?

On a side note, the FPV video transmitter also burned out but if I had to guess (correct me if I'm wrong) I don't think that that has anything to do with the above. The impact cracked the antenna off of transmitter and I suspect that this caused the FPV video transmitter to burn. If I'm not mistaken the antenna acts as a resistor to the transmitter and if you remove it the transmitter can fry itself, is that correct?

Thanks in advance!

Did you lose video before the quad hit the ground? If so it could have been a failsafe because of a bad signal or bad connection to the receiver. Its kind of suspicious that your vtx would "burn out" in a crash, even if the antenna broke. Its common talk that having an antenna disconnected or broke can cause permanent damage to a vtx, but in my experience it takes more than a few seconds to fry one. I've had antennas fall of in mid air, I've forgotten to attach one when working on the bench, but I've yet to fry one. What I would do is power up the quad and see if it flies. Start there and rule out bad escs. When you power up, first wiggle the lipo connection to make sure you don't have a loose bad connection.

I didn't have my video goggles on when this happened so I'm afraid I don't know about that. 

The vtx is an Eachine ET200 and the antenna mount on the topleft of the picture below as broken off. Maybe the mount itself already adds some resistance which makes a vtx not burn out right away when no antenna is connected? I have no idea. 
But you may be on to something about the vtx being fried beforehand, although I'm not sure that it would cause the crash. See, I read that having active damping / dampening light enabled can cause a lot of noise spikes on the power train of a copter. I had that enabled during this crash and I didn't have any intermediary filter between the main power train and the vtx power supply. People will add extra 220uF electrolytic caps to the +/- leads of their ESC to smooth this out, some ESCs already have them. My ESCs do but still, maybe not enough? So OK, given the context it might be the case that the vtx fried due to voltage spikes, but that leads to me wonder if the vtx burning out would cause a copter stall, having it crash to the ground?

By the way, I've flown a lot this weekend without any hickups with the LemonRX DSMX-compatible receiver on another frame which is completely hard-plastic, and what I did differently is that I added some big electrolytic capacitors. Googling on the path of brown-outs I read up a bit on where to place which kinds of capacitors. I don't have any golden rule yet but sifting through the posts I decided on placing a 1000uF 25V capacitor on the main power leads (where the LiPo connects to the PDB) and a 2200uF 16V cap to a spare servo lead on the flight controller. This should smooth out spikes and also fill in any dips which occur for instance by punching the throttle.
Reason I mentioned that the frame is hard-plastic is because on another forum someone mentioned that a carbon fiber frame could act as a faraday cage. My crashed copter was indeed a carbon fiber frame (well, it's Chinese so not 100% sure!) and the RX was inside of it. This might be a piece of the puzzle as well.