I work for a manufacturer of ultrasonic welding equipment. We supply ultrasonic welders to all industries. Changes in formulation dramatically affect the welding process, so when that happens, we often hear about it. The story goes like "we have been welding the same process for years and all of a sudden your welder stopped welding. After a long conversation eliminating the welder from fault, we will bring up the plastic. Customer swears up and down that their plastic is not at fault because there xyz specification is such that will not allow any formulation change. After a long argument, we finally talk the customer into finding old stock that someone has from the original product runs. Put the old part in, and it welds fine. Then the conversation goes up the ladder rather quickly. Usually what it comes down to is some purchasing agent sees as part of their job is to save the company money and allows a slightly different spec formulation without consulting engineering.
This is very common in the plastics industry, and I can tell you, virtually no company is immune. Even happens in the medical industry, which is much tighter on product control than the automotive industry.