Another way an error like this maybe could be produced... (Not being a printer, I may have an incorrect view of the printing process, so I may be way off base.)

I assume colors are screened on one at a time, with yellow being an early color. What if the screen was missing or malfunctioned during the yellow application, so that yellow was applied to the entire inlay instead of just where it was supposed to go? I also expect the inlays are printed in sheets, then die cut and placed on the chips prior to molding. So it would seem reasonable to assume at least one sheet worth of chips have this error.

The theory that a piece of yellow paper exactly the same color as one of the print colors was somehow used seems highly improbable.