Motor start at maximum speed while disarm, Quad takeoff and crash

the quad was on the floor, landed in stabilized mode, disarmed.
RC was turned off after landing , we were recompiling some code on the companion computer and after 5min , suddenly the motors started and the quad crashed in the ceiling. it lasted 1 second.
unfortunately i have no log, since it was not armed …

our code is based on V1.6.5

is there any other log somewhere in the Pixhawk SDcard that can help to understand what happen ?

software crash :
I had the info while uploading the last ULG in Flightreview.

it seems that the PX4 crash 13min after landing (4:30)

the date is not set correctly it happen today (feb 8, 2019)

hardfault_log] – 2018-10-18-04:43:21 Begin Fault Log –
System fault Occurred on: 2018-10-18-04:43:21
Type:Hard Fault in file:semaphore/sem_post.c at line: 118 running task: px4io
FW git-hash: 06c55cc20b448b43ac37342e702387a99e5ed5f7
Build datetime: Oct 26 2018 17:15:44
Build url: localhost