I had a Piper Archer from 1997 to 2017. Some of the things I've seen would send shivers down your spine. I used to fly over 150 miles for to get maintenance I could count on. (There was a pretty short list of things I was allowed to do.)
"I'll never know it all but I'm willing to settle for knowing where to find the answer!"
Parts changing is pretty common in all fields, what is worse is when it is regarded as part of normal planned maintenance and introduces unreliability. An example from the aviation industry but not on an actual aircraft instead on an emergency diesel generator at a major airport. A fuel filter change was scheduled every year but over the course of a year the generator would only run at most 4 hours on test with no load.
Of course the inevitable happened a major storm took out the power and the generator wouldn't take load. Flights were diverted and sweet smelling stuff hit the fan.
It turned out the fuel supplied to the old style mechanical injector pump by the mechanical lift pump was full of air bubbles.
The cause was of course the fuel filter change, the filter outer casing wasn't sealing.
The filter was the old style paper cartridge type, similar to used as oil filters on 1950's cars.
Most of us who changed oil filters on those cars learned the hard way that the large dia rubber O ring seal at the top of the filter although a new O ring was supplied with the filter the original O ring was best left undisturbed as to change it and get it oil tight was a pita.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
I dunno why, but I somehow thought parts changing didn't take place in aviation and other industries. 
