Example of "Mechanical Failure" in DataFlash log. Where to look from here?

After flying my Y6 900mm build successfully for a couple of dozen flights, it suddenly appeared to have a power failure of some sort, and fell straight down from over 100ft. This is my first build. I have nearly no experience in this hobby. I have attached a graphic showing the “Mechanical Failure” from DataFlash log along with the log.
I would appreciate it if someone in the disscussion could assist me in trying to determine the cause of this failure. Is it a loss of power? A pixhawk failure? Or software issue?
Thanks ,

2016-11-10 10-08-58.bin (942.5 KB)

Note your altitude stops at 58m.

That probably means logging stopped.

Your voltages look to be OK, but it seems your autopilot ceased to run. I would guess some sort of power issue:

Could be:

  • a short-circuit
  • a bug in ArduPilot
  • a plug coming loose

Does the autopilot still run?

Thank you for taking the time to look at and respond to my post.
The autopilot does run. I am not sure if it runs without issue though.
This is what I have found so going through the wreckage. The X8R RX will not connect/bind to the Frsky X9D plus RX any longer. I had to pull another X8R to continue. Then found out the buzzer is shot. Replaced it.
Moved the wreckage near the window in order to get gps sat. My bench is in the basement. For some reason I am not able to get MP to disable pre-arm prams. Anyway, it took a few minutes to get enough sats to allow arming. Of course compass issues. All six motors spun up. Here is the issue that I don’t remember from past bench testing. When I apply full throttle, motors spin to a high rpm, then on their own with throttle still full they back down to a much slower rpm. Don’t know what that’s about.
That’s all I have really done so far. There doesn’t appear to be any broken solder joints or disconnections of any wires. I have XT60 on the PM and battery. I always make sure they are connected securely and they were. It just quit and fell straight down.
I don’t have backup/redundent power to the FC. I plan to do this with the replacement FC which I have purchased. I have seen so many videos and post on how this is done, wish there was a definitive explanation.
I suppose I’ve babbled on enough. If you see anything here or have other suggestions that help, I would appreciate it.