What precautions are planned to prevent samples returned from Mars crashing and releasing organisms on Earth? and this answer to Why would bringing samples from Mars back to Earth be a “civilization-level changing capability”? cite the crash landing on Earth of the return capsule from the Genesis mission.
Despite the crash the mission was a success in that solar wind particles embedded in special materials were not seriously contaminated and could still be analyzed such that all success criteria were met.
That Wikipedia article links to this archived version of Space.com's Genesis Update which says in part:
Michael G. Ryschkewitsch, who heads a board investigating the mishap, said the planned test would have spotted the fatal flaw and prevented the crash.
"If the test had been done, the problem would have been caught," said Ryschkewitsch, the deputy director of NASA's Goddard Space Flight Center.
Officials at Lockheed Martin do not dispute that conducting the pre-launch test would have uncovered the error that doomed the $264 million missions.
Question: Exactly what was the nature of the test that was skipped? Was it simply a sufficiently long period of acceleration at 3 g to close the contacts or did it rise to the 30 g maximum anticipated? How was the acceleration of sufficient magnitude and duration going to be generated?
"bonus points" for information addressing why there wasn't a visual cue for the proper direction; wasn't there an arrow or something printed right on the G-switch?
Wikimedia: "Genesis crash site scenery"