I worked for a medical device company. We ordered stainless steel for implants (screws I think? Maybe pins) and I always fought to double check our vendors. The certification was faked, and the SS had too much nickel, which can cause reactions in a lot of people, especially if implanted. I got to rewrite our internal specification to state "no material shall be sourced from a Chinese supplier". I'd get routine calls about that line from our suppliers who wanted to sell us a new batch they just received, and didn't want to separate our stock from our competitors. It was frustrating and scary. And a lot of smaller companies didn't have the resources to double-check suppliers like we did. They'd take the manufacturer's cert at face value.

I've even seen packaging material that held an implant certified as nylon at a smaller company I consulted for briefly. I tested it and it was an epoxy paint, so it had unknown toxicity. The Malaysian company that made the packaging refused to take our calls once we notified them we knew they'd lied on the certs.