The mechanics......sorry.....engineers much used "Tested satis, no fault found" isn't good enough.
Wow, that was funny
Not quite as funny if you're the one operating the aeroplane immediately after such a "repair" and the same fault recurs.
I'd estimate a recurrence....ooh.....at least fifty percent of the times I've taken over such an aeroplane....probably much more, but I'll be generous.
Still, the problem then gets passed onto another base or another maintenance shift.
I guess each airline has it's own standards.....you obviously haven't encountered the bad ones Mr Fargoo.
Ooops! No.....just checked.......I see you're an engineer, not a pilot.