The vendors are in a tough spot. They don't make the parts. What they don't want to do is open up the flood gates to refund everyone whoever received a somewhat imperfect product from the beginning of time, but at the same time they should feel a responsibility to their customers and refuse to sell parts which don't fit. Surely they must get enough feedback from unsatisfied customers for the same problematic parts. Maybe not. I am sure a lot of kooks call to complain about parts which are perfectly fine, more so than calls from polite and sane folks like most of us here on Stovebolt.
I have a good friend who has a close working relationship with one of the major vendors which is one of the sponsors of this site.
I have been intending to see about opening a dialog with this vendor for the purpose of providing input from folks on this site about specific problems with specific parts purchased from them in the recent past. The purpose being, to give them the opportunity to demand better quality control from the manufacturers of the parts, or to discontinue selling these bad parts.
Carl