Copter didn't disarm on landing, then flipped over

ArduCopter Copter 3.3
1

Today I had an incident which I had several months ago when I first tried APM:Copter:

  • I landed in POSITION HOLD mode
  • put throttle to minimum
  • however even after some time it didn’t disarm
  • then I put stick into disarm position => no effect
  • after some time it started to spin two motors faster and flipped over

I’ve uploaded by dataflash log here: 1drv.ms/1oVbQfI , can anyone help me understanding what happened and how to avoid it?

2

Same effect with 3.3.2 and 3.3.3.
Not with 3.2.1
Copter hurt my finger dramatically.
The safty button does not disarme, only stop the motors.
After pressing the safty buttton again, the motors starts immediatly with full power.