These "fenestron" stall situations really puzzles me .... (I'm not rated on the EC120)
I've flown several thousands hours on different variants of the 365 as well as a few hours on the "Gazelle" in various countries and operating conditions, including air work....and it is something that I only once "might" mildly have experienced on a 365C when taking off from an offshore rig.
It is a matter of fact that a "fenestron" becomes efficient at the end of the rudder pedal range,when countering an increasing torque, maybe is it what pilots experienced on conventional tail rotors can analyse as a tail rotor stall or an LTE...?
Normally this particularity is highlighted during the conversion course