Two thoughts:
> they typically will not be thinking they are doing anything wrong. They are just testing if you notice and if you do not they will say it makes no difference for you but saves them costs.
This is how children behave. Still feels like you’re rewarding bad behavior. You’re enabling them.
I think it’s more that you’ve valued the low per unit price over having a healthy contract. Your vendor is incentivized to make all of their money off of externalities and your company think it’s cheaper to outwit them than to demand QC on their end. Whose brand will be sullied if you miss some of these units and a customer finds the spyware? Not theirs.
And second thought, shouldn’t serial numbers be coming off the line in ascending order? The kind of work they are doing would require taking parts off the line and putting them back later so odd lots of SNs are the ones you need to verify.
You could also be mandating how many boards are allowed or that the SNs go on early in the build process.