Well, Stan, are you sitting down?
If Dan Reid walked in I'd be shaking in my boots wondering just what financial motivation was at work.
A process change
can be just about anything. Moving a piece of process equipment, different supplier of a material or subassembly, you name it. The question is what is considered a critical change and what isn't. And that definition is entirely up to your company to decide. One client of mine produced an array of products and much of the process equipment and assembly tables were mobile - they set the plant up nightly for the next days planned product. Since the products were mixed and several would run a day, the place set up to produce the assembly could be in several places. Since most was assembly equipment of a simple nature they did not consider changing location critical.
What ever you decide to to, get some kind of guidance from your US automotive customers' supplier QA folks as to what they (with consideration to YOUR company processes and what you supply to the US automotives) will accept (which you will find nearly impossible).
I wouldn't think blocking off a cavity would typically be a process change. But if the parameters were critical enough and let's say you have heated molds and a heated input, it could be argued that blocking off a cavity would throw off the thermal properties of the mold requiring requalification of the mold.
If you found containment marks as cause for rejection it shows a lack of communication with the customers. In the past when I went into containment I contacted customers about the problem(s) at hand and my intended identification scheme to preclude rejection. I wouldn't think a
PFMEA change or control plan change would be driven by a containment mark but if you're in containment you would be looking at both the PFMEA and control plan any way.
I know this answer is not what you wanted to hear - there is no black & white, but here again logic plays a big part as does making sure all communications with your customer supplier QA folks is well documented - even if you just get a verbal from someone. Write down their name, the content of the conversation and the date/time of the telecon.
Isn't this stuff just dandy fun???