Quadrotor crashed caused by rangefinder and motor readings based on datalog analysis in mission planner

I have the problem of quadrotor crashing a second time. However, this second crash was very serious, because the motor 2 came off while the ride was in the air, causing the ride to spin out of control and finally fell down 9 meters high. Before experiencing the crash, the quadrotor suddenly rose itself from a height of 3 to 9 meters, even though the pilot had lowered the throttle. Our assumption is that after viewing through the telemetry log, the rangefinder reads 3 meters while the altitude reads 6 meters. After that then the motor 2 is off.

Are the assumptions we have made correct?
Here I attach the datalog from our mission planner.

Altitude (both calculated and barometer altitude) roughly follows pilot RC input as expected.
The problem is vibrations about 60% of the way through the flight, probably when the motor is coming loose. Z axis vibrations go over 30 and the copter starts rising - the effect of z axis vibrations is the copter thinks it is falling so motor outputs are increased.
You’ll see every time the Z axis vibrations went over 20 the copter rose - until right at the end when the motor must have come off.

Rangefinder altitude is noisy near the end, so you might have it configure wrong, but I dont think it’s the cause of the problems.

While you fix everything from the crash :frowning: you should update to latest stable firmware. Make sure you pick Pixhawk1, which I think you did in the past too.
Unfortunately that Pixhawk seems like it might only have one IMU. You can check in MissionPlanner HWID (upload a screenshot here). You should probably set this anyway:
If it does only have one IMU then consider the purpose and reliability of this copter versus the cost of a better flight controller.

And before the next test flight, connect to MissionPlanner / Mandatory / Initial Parameters
Put in your prop size and battery cell count, also select “Suggested settings” and then accept everything it offers.
Plus set these:


And don’t double post for the same issue. It’s a waste of help resources.

Also here’s the altitude/throttle graph I meant to add before.
I added an unused RC channel (blue) to give the straight line across at 1500 PWM as a reference for approximately where centre/hover throttle should be.

thank you.I could fly again with my quadrotor safely.