I have a serious trouble with IrLock with cube 4_0_7. I fly with X8 copter (17kg TakeOff Mass)
I trigger Landing from PosHold at 45 m AGL. Copter lover slowly and (at approximately at 35m AGL) rapidly change position to valid (over the beacon MarkOne). That rapid movement are dangerous and almost become to crash. PLND_EST_TYPE Kalman, but changing to PLND_EST_TYPE Raw Sensor are much worst and much dangerous to me.
You need to limit the copter acceleration and/or jerk to keep that under control.
ArduCopter 4.1.5 is better at limiting that than 4.0.7. So update and change the parameters.