No wonder China keeps screwing with you guys. You aren't supposed to eat that cost! Write a PO with tons of fine print that says "We will disassembly units at random for compliance inspection. Non compliant products will be returned at the suppliers expense." And then add a clause that says ">3 non-compliance events in under # months will result in the entire PO (10 or 20 units) being returned and all contracts cancelled."
I cannot believe you are getting screwed by a company you choose to do business with and yet you eat cost to ensure they aren't screwing you. Just get a new supplier! Do on-site inspections at their facility. This is nuts.