Did you have the prop guards? I've flipped mine a couple times with the prop guards on, but never with them off. Maybe you caught an ill timed gust of wind.
You think turning off the collision avoidance doesn't save any battery? I'm not convinced. It may not be much, but it has to cost something otherwise it's poorly implemented.
Anecdotally it feels like I get more flight time when I turn off all the nanny-software gimmicks and fly in sport mode. I should start collecting data to see if this is true.