Problems landing a quadcopter X

Hello guys,

I have a custom made quadcopter X as shown in the link below, running ArduCopter 3.6.9.

A few weeks ago I had a problem during landing it in Loiter Flight Mode. When the drone touched the ground, it did not recognized the land complete, accelerated the motors, tilting the vehicle towards, damaging propellers 1 and 3. The vehicle did not have a downfacing rangefinder in that occasion (flight registered in log_1 file).

Today, I was flying the drone with a SF11/C lidar connected thru I2C in I2C2 Port, and again had a bad landing, this time in RTL Flight mode. Again the vehicle did not recognized the land, unstabilized and this time I had damaged propeller 4 (flight registered in log_2 file).

Could someone help me to find the problem please?

Link to flight logs:

Link to crash video 1:
Link to crash video 2:

Try setting these parameters and see if it helps
WP_NAVALT_MIN 2 (or similar, maybe 3)

I couldnt see anything really wrong though… I thought perhaps vibrations but that looked OK.

Unrelated, but I also set these parameters:
ARMING_VOLT_MIN 11 (no point arming if voltage is just going to trigger failsafe within seconds)
MOT_BAT_CURR_MAX 60 (for safety of your power system, a value your battery and power system could safely handle)

Thanks a lot for the advice Shawn!

I set the first three parameters and I will test and hope to not have more crash incidents.