"Specifically, the Ariane 5's greater horizontal acceleration caused the computers in both the back-up and primary platforms to crash and emit diagnostic data misinterpreted by the autopilot as spurious position and velocity data. Pre-flight tests had never been performed on the inertial platform under simulated Ariane 5 flight conditions so the error was not discovered before launch. During the investigation, a simulated Ariane 5 flight was conducted on another inertial platform. It failed in exactly the same way as the actual flight units."
That's exactly how Ariane 5 crashed in 1996:
https://en.wikipedia.org/wiki/Cluster_(spacecraft)#Launch_fa...
"Specifically, the Ariane 5's greater horizontal acceleration caused the computers in both the back-up and primary platforms to crash and emit diagnostic data misinterpreted by the autopilot as spurious position and velocity data. Pre-flight tests had never been performed on the inertial platform under simulated Ariane 5 flight conditions so the error was not discovered before launch. During the investigation, a simulated Ariane 5 flight was conducted on another inertial platform. It failed in exactly the same way as the actual flight units."