Rotor stops for no reason and falls like a brick ...

First things first, I love this heli, great job guys

I'm very new to helis, have only 100+ hours ...

But not sure what's going on here, during take off the rotor just stops and I just fall like a brick.

This only happened at the free Propstrike studio's Machmell Fisheries helipad. I did not experience this elsewhere.

X-Plane is 11.30, OS Ubuntu 18.04
OAT was 4 degree. Carb heat on/off does not matter.

Here is a video:

drive.google.com/open?id=1tzc24ROVgQbfXZ_48IEASFFFonJPWvjt

and one from inside

drive.google.com/open?id=1h7jtXtUmQbngWKWgliOEkCxMjmkdy_Vf

update 1:
In Failures I can see: "Engine separation 1 - Failed "  

Cheers