Unplanned upgrade of my Y6 frame

I'm going a bit out of order here, as I still haven't written up the build for either my MultiWii Quad or original build of the 3DR Y6.  But this one is more interesting.

I'd flown my Y6 a good number of times, even several in quite windy conditions at Emerald Isle, NC.  Had never had any problems with lack of control or anything.  Last weekend, I finally got around to adding LED strips to the legs to help with orientation, including a 12V regulator (I usually fly with a 4S pack and the LEDs aren't intended for that high voltage).  While I was at it, I hooked up an additional JST connector to my power distribution board to power my gimbal.

After all that, I did a quick test flight in my backyard and everything appeared to be working properly.  So after work, I stopped by the park to try a real flight with some space to maneuver.  I was in a bit of a rush, so didn't connect my tablet or wait for GPS lock, just intending to fly around a bit in Stabilize mode.  

I took off and everything was working fine for about 20 seconds or so.  Then it started flying away.  I tried turning it around to head back towards me, but it kept flying in the same direction.  I pretty quickly ran out of space and crashed into a fence.  The carnage was pretty impressive:

• Broke all 6 props
• Bent both mounting plates for the gimbal as well as the RC connector (though it still works)
• APM and GPS sheared off the mounting plates
• Broke a bunch of the nylon screws for the landing gear and lost a spacer
• Broke all the standoffs for the GPS/accessory plate
• Cracked the carbon fiber base plate and it broke in half

They don't appear to sell replacement parts for the 2013 Y6 frame anymore, so I ordered a 2014 frame kit.  Just swapped out the base and top plates, though - pretty sure the legs are the same and there didn't seem to be much interesting with the new APM or accessory mounting plates.

As to what went wrong, I'm still not clear.  I don't have any experience troubleshooting APM logs so will need to figure that out.  My guess is something to do with the compass - in retrospect, it was behaving as if it was in Simple or Super Simple mode, but I don't even have that configured as an option right now.

Update: Replaced the top and bottom plates with new ones from the 2014 frame kit and it's back in the air.