This guys factory is just across the lake from where I live and this is painful to watch. Both Alibaba and the general local industry (metal fabs, train shops, etc) have high degrees of expertise in supply chain verification. You can hire (heck even bribe) experts along the way to reduce fuck ups. The video contained no mention of any audits, any additional paperwork beyond some pictures.

I once had a company that procured very simple electronics (fingerprint readers) from Taiwan and due diligence included travelling there, meeting every single person in the engineering office in person, then touring the contract factory where this would be built, then negotiating shipping and even driver development details.

This took all of one week and the price of a few plane tickets. We didn’t have the cash for professional auditors. In the end we got a product that worked, and even at a lower price (negotiating at a distance is not effective).