ET, that's a good point. BUT ......... KM's observations are, perhaps, not entirely valid though morally laudable. Here's a short, but true anecdote that illustrates my point.
20 years ago I was privileged to sit on a panel of Senior Technical Management for Bell. I made the point that it was rare for the aircraft, per se, to have a warranty problem, but the vendor items created all hell and mayhem with the customer, who, not unreasonably held us, the seller, responsible for fixing the problem. (This was when I was Ch Eng at Alan Mann)
The executive director of customer support was a great chap called Bruce Camp, and he picked up on the point that was simply if I complained such a comment it would be 'less-than-significant'. BUT.... if Bell complained about the total lack of meeting a reasonable MTBF then something would be done about it. Thus Terry Jeffcoat's responsibility for warranty was expanded to include monitoring of any vendor item's reliability. Result!
Thus the responsibility for such 'vendor items', particularly to include RK, lies with the TCH, not the certifying agency. And the TCH has tremendous clout (contracts and money talks). I've been away from the politics with OEMs for some time but I think the principle is valid. FWIW in another life I had exactly the same experience with Agusta, more pressure and Anglo-Italian relations at an all-time low for a while. However the end result was worth the pain
Just FWIW - VFR