Procuring subcontract precision engineering for medical device components can be a minefield. Sourcing the right fit for your supply chain is far from easy because of the sheer number of players out there. Many claim to be specialists in their own particular sphere of CNC machining (while still taking on plenty of non-core work). And you will know from experience that some precision engineers are more precise than others.
You're having difficulties with a precision component for a critical medical device. The part won't fit the assembly. Or the finish isn't right. Or the quality/consistency is hit and miss. Or any number of other issues. But your existing supplier – who perhaps has been reliable up until now – is pushing back: they did "exactly as instructed", they protest. They followed your drawings/CAD models "to the letter". So what went wrong? And how can it be fixed quickly and cost-effectively? You want a second opinion – is the issue with the supplier, the drawings or both?