Many years ago a UK company imported an overhauled Hiller from the states as they believed they could get a cheaper aircraft there.
To get a UK Cof A it had to undergo main gearbox inspection to comply with a UK AD brought in following an fatal accident to a UK aircraft.
The results of the said inspection were not pretty especially as the aircraft was "overhauled" and the CAA became involved.
They then asked the question who overhauled all the other components fitted including the engine.
Sadly the answer was the same company and the result was that the whole drive train had to be inspected and recertified at enormous expense relative to the value of the aircraft.
Caveat Emptor