If the programmed path is off by a few centimeters then it won't be an accident. The robot will scramble the brains of whoever is sitting in the chair every time. Also who knows when a mechanical component will give under pressure? It looks like that robotic arm is really made for soldering , not heavy lifting. Accidents happen all the time in systems people think are foolproof.
I love people like that - they are the sorts of adventurous people that make my job interesting as opposed to people moaning about man-flu.
I can just imagine turning up to the scene of the accident and seeing a 12 foot streak of blood and brain tissue smeared across the floor, then trying to work out what they were doing.
Then calling the police. Not for any legal reason, but because they deserve a laugh as well.