Well this has probably been discussed before, but, my searching unveiled nothing.

The Basics:

Flying at sunset, temperature 12degC, no wind

APM2.5+ with 2.9.1b

Y6 running Turnigy 950kv Motors & ESC, 4S Batteries.

This frame had done around 50 minutes of flawless flight testing inside and out, very stable, very powerful, no dramas... till tonight, I sent it up for some photos of the sunset, and I noticed the props started to sound a bit off, when attempting to descend the frame seemed very reluctant to do so, I was up maybe 30 or 40m (100ft ish).  As it came down it started to YAW despite no rudder input, I noticed as it got closer that what appeared to be the front right lower motor was slowing down and then stopped all together, at this point flying got interesting and I made the call to bring it down fast and hard rather than risk loosing it.

Hard it landed, bounced up about 1 meter (3feet ish) and landed on it's head.

When I got home I removed props and tried to power up to see if the abhorrent motor was now responsive, but the board didn't want to power, a quick flash of the Blue led then it went out with a dim flash of orange beside it and only the green led by the gps port remained on.

Once getting home I tried to power it up via USB to download the logs but still flash of blue, dim orange and then just the green, accompanied by a surprising amount of heat near that green LED. The source of heat circled in this pic

Does anyone have any thoughts on what could be up? I have a spare board so not really fussed on loosing one, but I'm very interested to see the Log to work out what the heck happened, a fault with APM, or maybe the motor/esc.

I can see that the Reset button must have been mushed into the board and bent the housing, but continuaty testing showed it to still function properly... though I guess the fun with multi layer boards is god only knows what is sitting under it that might be crushed now...

Thanks for any help.