Be very careful what is said about Fenestron Stall, to newbie's.
There is a phenomenon where the "acceptance angle" at the shroud permits the tail rotor to accelerate significantly to such an extent that the aircraft will rotate well in excess of its operating limit. (The cab can rotate around its axis atleast once or even twice IN SECONDS before the uninitiated pilot knows what is happening).
As (quite rightly) mentioned, this is NOT a design flaw, or LTE. It is, how shall we say: "a shrouded tail rotor aerodynamic phenomenon" which ALL shrouded tail rotor pilots MUST be aware of.
The phenomenon is easily overcome by applying FULL and persistent opposite pedal until the spin stops...and it will.
The problem with the great unwashed is that IF they are not aware of this, then it will certainly take them by surprise and probably lead to them losing control of the a/c.