Problem with RC4....land keeps landing, doesnt disarm

suspect an altitude issue as the desired altitude keeps going down for some reason even thou barometer indicates 0 altitude, the LAND command persists not disarming the copter…log attached in link below

https://drive.google.com/file/d/0B22Vj25Xii1rUTBaRTluekNRNGs/view?usp=sharing

Trying turning GND_EFFECT_COMP