Are you able to trace reported product back to the source - that is, can you determine if the problem product is made by your organization or by your parent company? If you have that ability, while it may not directly impact your customer(s), you'd have the data to reporting on a nonconformance rate by supplier. Unsure if it will change the behaviour/output from the parent company, but it will give your own team a sense of "hey, it's not us...and when it is, we make it right."