Another crash EKF2 latest stable. Disarmed mid flight

Just had another crash today with Latest stable EKF2. From the log messages I can see that it had disarmed itself during the flight, after it detected the land. So when it stopped logging, the copter started to fell down. I didn’t find anything from the log that could disarmed it like that, but I might take a deeper look, likewise check the source code for disarm logic.

Some details about flight/takeoff: There was a try to arm when safety-switch=off, then we turned it on and arm copter, takeoff. In the beginning of flight we made a slight changes in attitude PIDs and it was flight afterwards without any issues for another 5 min. We also carelessly changed MPC_Z_VEL_MAX_DN parameter, even thought it was written not to change it in QGC parameter’s comment - we noticed it after the crash.

Frame: Copter X4
Firmware: d017514d59a0c1b7467c89c45ebe106080fad102, Latest stable EKF2
Conditions: Almost no wind
UAVenture log:
Link to px4log, QGC log, other files on SDcard:

Would appreciate any help on that,
thank you in advance!