Looks like either operator or manufacturer error. He was a larger boy, and there is a significant gap between the bottom of the restraint and the seat - obviously large enough for him to slide through (is that called “submarining?”)
Maybe the operator didn’t check the restraint - but I would imagine on a ride THIS new there are surely sensors indicating if a harness isn’t closed properly, and it would probably be impossible to start the ride if his harness wasn’t clicked fully, per the computer’s standards. But that leads me to believe that the restraint WAS clicked “enough” and the manufacturer simply made a grave error in defining was “enough” was.
I don’t think the harness itself FAILED, per se. In the video after the incident, you can see that the harness is still locked in the closed position.
Time will tell, but that’s my guess.
I feel bad for the worker - people are already ready to hang him by his toenails because he was making a joke about “check the seatbelts.” It’s an old, tired joke in the theme park industry for rides that don’t have seatbelts - just a way to (usually) have fun with the riders. I’ve heard it on Everest, I’ve heard it on Tough to Be a Bug, I’ve heard it on the Safaris, just to name a few. Normally, it’s harmless, if not annoying. In this case, I hope it’s not incriminating. I mean, maybe the worker will be found at fault for SOMETHING. But using a common, dumb joke shouldn’t be used against him.
Bet that joke won’t be allowed at any rides in the area from now on, though.