Motor failure test

I was tested one motor failure by a hexacopter, I set the parameter MOT_YAW_HEADROOM to 0 to increase the priority of maintaining altitude.
But in the hexacopter test, Maintained the yaw vehicle and had an altitude drop of about 20 meters.
Why couldn’t it maintain the altitude instead of control yaw?
Log file:

The control loops have been improved in ArduCopter 4.1.3.

Yes, but I saw movies like this in which the vehicle maintains its altitude in the lower firmware, I wanted to know if it has a special setting?

Arducopter has no “special settings” for this.

Did you find the reason your hexacopter did not maintain altitude?

Our Hexacopter flies quite impressively with one motor damaged and only four providing thrust. it still flies missions for several hours now (until the replacement motor arrives) to rescue row deer fawns.

I’m deeply impressed by the work of the Arducopter community!