Dear Lu,
Well I did get compressor stalls, like the ones you get when you roll the throttle on too quickly sometimes. And let me see if I understand this correctly, you are telling me you have to change the entire driveline and dynamic system? I have gotten compressor stalls many times at this altitude and I have never seen anything having to be replaced except maybe the FCU for not functioning properly.
On how the blade hit the fin, well this is pretty simple to do in the L4, things that can cause a "fin hit" can be, lowering collective too quickly after a touchdown auto, pulling cyclic back beyond neutral during a running auto landing, high wind gusts during starting and shut down, I guess its sort of "easy" in the 206L series, and the interesting thing is that if your barely hit the fin, that means your were about 2 inches away from hittng the TR driveshaft covers (boom). The transmision does have that Nodamatic system which makes flying the L series sort of like riding a magic carpet in terms of smooth ride, but it does allow for some limited movement, but not enough for the blades to contact the fins, the blades need to be flexed down for this to happen.
Tomorrow I will take a pic of a flapped down blade in a 206L and you will see how close the blade gets to the fin.