Reminds me of the story I heard about a new ride at the (then) Marriott's Great American in Santa Clara, California as told by a park engineer at a special event for high school science students. He talked about their shuttle loop ride called The Tidal Wave which was made by a Swiss company. The park was testing it before allowing any people to ride on it, but they generally used sandbags to simulate weight. If it worked properly then the bags wouldn't fall out. They asked the manufacturer (whose technical rep was onsite during the installation and testing) if they could load it this much, and he was a confident "absolutely yes". So they did it, and on the first attempt it reached the top of the loop, stalled, and the bags dumped sand on the track, at which point it dropped and then the wheels ground the sand into the track and wheels.
So they're back cleaning this mess up, and where they needed to repack the wheel bearings which are likely contaminated. But nobody told them what grease to use. They used what they had. What they didn't realize was that they spec'ed some really heavy grease and what they used was might lighter. So they started it up, it went through the loop, and then all the way to the top of the shuttle where it knocked off the barrier at the end. Eventually they got it right, but that was a case where it was definitely going too fast.