I had never heard of it before. Apparently it's one MORE safety-related issue swept under the rug.
The loco manufacturers use contracted-out parts from teeny-tiny manufacturers to avoid liability. You cannot tell me, for example, that over at GM-EMD, in the day, AC-Delco couldn't make a better heater than Prime, Incorporated. Or that they needed to rely on glass from Sully, when GM is the largest maker/user of safety glass in the world.
No, they bought these off-brand parts to deflect liability in case of injury or failure.
This is the flip side of it. In attempting to deflect liability, they've exposed workers to REAL danger. GE can make its own diesel engines, but cannot weld up an air tank? That they have to go with some supplier who's a workshop in a garage somewhere?