Well, now it's my turn. After dozens, maybe hundreds of flights of my APM, today in my pre-fpv RTL test, the APM decided to throttle up to maximum, go max pitch, and plow deep into the earth, damaging or completely destroying everything on the quad.
I thought it was just coming home (RTL) somewhat fast and would stop after overshooting, and land at home, but it went directly through "home" and just kept accelerating until it did a pile driver into the dirt.
Time between it looking normal and planting itself was about two seconds, so there was no time to react. I kept thinking it was going to correct itself until it was to late. Usually, it'll come home, pause and when it starts to land, I'll go back to stable and fly either a mission or fly manual.
I've checked the logs, and it goes 100% throttle out, with a stable throttle in. It shows the pitch and roll increase and so on. As far as I can figure, it decided to fly into the earth. I had 10 GPS sats. In the logs I saw them drop and come back which is the only odd thing I see and in the KML file I can see the APM thought it was a few feet north of the crash crater, but not abnormal for GPS accuracy.