Thank you for the link. I am familiar with it.
To be clear, we do not use Material Variants at all. I would like to, but the users have to this point been reluctant to change processes.
Each and every sales order line item for one of our machines is configured and built using just the configurable material (KMAT). I believe I was careful in using my terminology and never said "material variant". But forgive me if I have not been clear.
You have stated the problem correctly except for the fact that the new customer requirement resulted in a new KMAT on the sales order, not a material variant.
Can you please advise whether this makes a difference in this case? It appears as though the equipment is tied to the original entry and cannot be changed regardless of whether the difference is a configurable material or a material variant. Is that so?