This story takes place in Calm Wind's Wonderverse, between Act 2 and Act 3 of Piercing the Heavens, though hopefully it's understandable on its own.

"The impossible happened... Rivet started making mistakes.”
“Doesn’t everypony make mistakes?”
"Even if ‘everypony makes mistakes’ was a legitimate excuse, most ponies mistakes don’t almost injure ponies, and definitely don’t almost kill ponies.”

Rivet is, before anything else, a genius. A master of machines and the lead engineer for the Wonderbolts, he's the first pony you go to for all problems mechanical, from inventing new training equipment to rapid repairs. It isn't much exaggeration to say he's one of the rivets holding their base together.
They leaned on him so much, it seemed only natural that he start to buckle under pressure. The machines he designed to get the Wonderbolt recruits up to speed have started to malfunction, and ponies have narrowly avoided getting hurt. Now he's under probation, forced to take a break from his work.
No one is listening to what he's saying.
No one is seeing that a saboteur is on the loose.
With both his job and the well being of the Wonderbolts on the line, he calls the only person he can rely on to solve the case. He calls his old friend and rival, ex-detective Keen Eye.