Strange ground effect on landing

[some1]

When I perform a slow approach, the helicopter bounces back into the air at around 7 ft. Not touching collective, and the aircraft goes from slow descend to climb at a rapid pace, and keeps climbing past 70 ft. On the second approach I need about 10% less torque to maintain descend speed. 

In this track at first I need 91% torque to hover at 8 ft, then set 88% torque to descend, but instead of descending the aircraft starts climbing. And on second attempt 78% torque is enough to maintain descend speed. 

oh58land.trk

[Kinkkujuustovoileipä]

This is known, we are investigating it.