We have a high performace copter a bit underpowered.
In one flight while RTL and descending it seems it get to a point were motors were very high and the Attitude VS Altitude algorithm entered in action. The copter accelerated its decent and hard landed. Not a lot of damage.
We think it was the Attitude VS Altitude (stability patch) but could it be another thing? It can be seen some oscillation in the battery voltage prior to the start of the descent in the RTL.
It was a windy day.
On top of that, Once the copter hardlanded, we take off again and it was flying ok.
So apart from lowering the weight of increasing the available power, is there something in the parameters that could prevent or improve this to happen?