It starts out as not enough TR thrust i.e pedal
As it progress's and the aircraft starts to drift off to the left and you think he is going to straighten it out as the fin starts to become effective, the TR is at max pitch and being pushed perpendicular to the airflow (think vortex ring) and also possibly some wake now from the main rotor has joined in, the power required to keep the tail rotor turning helps to top the engine out and you can hear the loss of RRPM.
This is a trap on L3's. If the governor was a little dopey or the RRPM was not at the top of the green to start with.
Begs the question about the departure as it nearly had OGE hover capability.
Technique was definitely lacking. Ticked all the boxes to get LTE.
Spent a day with an L3 once pouring concrete at 9000' DA. Trick was to keep full left pedal and steer with the collective. Don't fly sideways to the left or let the nose drift right though.
Helicopter is definitely too big for the TR!