I'm new to this site, and also new to the Mavic's, but I've been flying drones and RC planes and heli's for many years. And while I don't know the full details in this case, I will say that 95% or more of bits falling off flying machines of whatever shape could have been prevented by doing a proper pre-flight inspection.
Before I fly my Mavic Pro, I check that the arms are properly in place and that there is no play in the hinges. I check that the battery is securely in place. I do not fly if my controller has less than 50% battery left or if the Mavic has less than 65%. You never know you might just need those extra few %, especially if the wind is blowing higher up. To check the props, make sure that the spring is doing its' thing just push down lightly on the prop hub, it should bounce back immediately. if not, the spring is gone and the prop will come off. Check if the prop is sitting square on the shaft, if not one of the 3 tabs has broken and the prop will come off. Check that the tabs are engaged properly by trying to turn the prop by hand while holding the motor.
This whole process takes about 25-30s at the beginning of each flight and can save you mega $$$$$.