I have seen the video. It’s very distressing.
The shoulder harness was designed to be fully down. When in the fully locked down position it would apply pressure on top of the shoulders and over the chest, (stopping you going up) but the bottom of the harness would also be right down over your groin, at an angle greater than 90degrees, stopping you sliding down and out and pushing your bottom into the back of the seat.
When I have been on similar rides in the UK, there is also a failsafe buckle that comes up between your legs and clips into the bottom of the harness, so even if the harness unlocked, it would not fly up very far. I can see on the video that other riders do seem to have a buckle in place. In the UK, I have also seen this sort of a ride with a ‘double’ harness - a solid T lap bar that sits between your legs, and then an over the shoulder harness that comes down on top, with a fail safe buckle connecting the two.
The shoulder harness for this poor boy did not even come down far enough to be covering his stomach, let along reaching his groin and thighs. It was left resting at an angle of 45degrees, perhaps a little more, resting on his stomach and abdomen. The fail safe buckle is not in place and probably did not reach.
I cannot for the life of me understand why the attendants did not spot this or taken action if they did spot it. Whether they didn’t check, or did not understand how the harness is designed to operate and therefor did not understand the implications of it sitting at such a high open angle, even if it was showing as ‘locked’.
I find it hard to believe the harness was able to ‘lock, at such an open angle, but even if it did, it was incapable of performing its function of pinning the person down and back into the seat at such an open angle. And with no fail safe buckle in place there was literally nothing preventing him from sliding right out of the bottom of the harness and seat, which is exactly what happened, at height and at a speed of around 75mph. He went up still in position, but as the ride came back down, as the break was applied, his body continued its downward trajectory and there was nothing to stop it.
According to witnesses, he did voice concern that the harness was loose fitting but was told it was fine. His friends said he was so concerned he asked them to tell his family he loved them just before they went up.
In my opinion, it was a completely avoidable accident and should never have happened.