I noticed that, VT_ARSP_BLEND description includes a misleading information: "Set to 0 to disable".
When it is set to zero, it actually blends between MC and FW actuators starting from 0 m/s. This caused a hard landing on my platform due to not having enough control authority on the aerodynamic control surfaces at low airspeed. Then I reverted it to a safer high value.
My flight log can be seen here.