The manufacturer is the manufacturer and proof of purchase from a stocking distributor should suffice.
When I are in the midst of a lower end assembly, I do not have the time to unassembled what I have done, call the "supplier", wait for a RMA, ship the goods back for examination, and wait for reshipment.
What a week or better?
They should be embarrassed for a quality error of this kind(or disgruntled employee action) and fixed it. Period - end of problem.