Apm firmare 3.2.1,sudden rise of altitude in position hold mode

I am using Apm 2.8,firmware v3.2.1.
The quad takes off in stabilize mode , then switched to altitude hold mode hovering stable at 30 to 40% of throttle, then switched to position hold mode where it hover stable about 30 seconds approximately at 40 to 50% of throttle at altitude of less than 3m.

  • But suddenly quad starts climbing so reduce the throttle input approximately 20% but still quad climbing nearly greater than 15m altitude so switch to stabilize mode and reduce the throttle again. but for a fraction of seconds quad lost all controls then starts descend fast, again got the controls back but quad was very unstable and crashed while landing.
    One of the motor bullet came out (couldn’t predict that whether it came out in the air or after crash)
    i couldn’t figure out whether its hardware of software issue.
    i have attached log file as well.2020-03-04 12-42-03.bin (333.1 KB)

This can often be a result of high vibrations but you don’t have enough logging enabled to determine that.

It will become more and more difficult for you to get technical assistance with that obsolete Flight Controller.