My last career stop was as a Supply Chain Analyst for a company in the automotive industry. I had responsibility for a low volume radiator, maybe 5,000 units annually. The supplier was sold to a larger company and they wasted no time no time notifying us they would no longer supply the radiator. In researching history, they were the 3rd supplier in 10 years.
Suppliers like these don't want low volume production. They take the business when they have available capacity and drop it when they need room for a better customer. I'm sure you have heard the stories about how the auto industry pushes its suppliers around. In many cases, there are few suppliers worldwide with the capability of producing the quality and volume you're looking for and they know it. They can be just as tough.
BTW the radiator was for a vehicle still in production. When the vehicle is no longer in production, it can be very difficult to convince a supplier to continue to service it. They may offer one last production run to cover the service life of 10 years. Cost is often higher. You have to service it so you're stuck with the inventory. Getting to be very common with parts having a circuit card, like fuel pumps, key fobs.
HBC is in no position to dictate terms to a supplier of radiators.
