Re: Your current system
we keep track of lot number which roll was used to die cut the circles from. that is stamped on the traveler
the problem I have, I cannot trace a faulty product to the person within the production in the case of complaint-to do the corrective action properly
When conducting root cause analysis, it is best to look at the process first... what in the process allowed the operator to make the mistake? If one person can do it, then they all can do it. So... the corrective action is to correct the process utilizing your quality tools like poke-yoke, kanban or some other more appropriate tool.
Have you looked at utilizing Ishikawa (Fishbone) diagrams to determine potential causes of the error and then examining each of those causes to find the root cause? That might help also.
Unfortunately, the real difficulty comes in when you examine the process and the process is robust, yet, people still make mistakes.

Then it comes down to an individual level. But this should be the last resort.
Hope this helps!!
Cheers!
Michael