Well, I've watched the video, and I'm not entirely sure what caused this, because I don't know the windspeed, the magnitude of the pedal input, the density altitude, the mass of the aircraft, the pilot's degree of caution in causing an overtorque. You know... the et ceteras. Perhaps someone looking at an image of a helicopter the size of a flying termite can draw more information from this clip than me, or perhaps they have greater skill.
But then again, my experience in Dauphins is limited to a mere 4000 hours in the 366G1, 365N, N1, N2, & N3.