Mechanical. Electrical. Electronic. They can all fail can't they? Are any of them failproof? Which is the most dependable? Why?

I was a motorcycle mechanic for several decades. One of the reasons I got outta that business was the problems I had diagnosing the new electronic systems. The manufacturers gave no information at all. They said; "replace the component with a known good one".  Well now, that meant guesswork. Since the component could cost $500 or more, I couldn't just order a 'suspect' part and hope it worked. Customers didn't wanna have their machines sit in the repair shop for months while you experimented with expensive parts.