We lay out all cuts, and use blue crayon on the inside of the cut to designate
the cut. On out of square timbers (which we make each other aware of) where we have layed out snap line, it's the cutters responsibility to set the cut of depth to the shallowest cut. We operate as a collective group and profit share, so mistakes are rare.
If this guy/girl is good, keep him. I doubt he'll make the mistake again. Eat the profit loss and have him recut. The lesson has been learned, and he'll be better for his mistake. We've all done stupid stuff, and he was probably just trying hard to do the work in a quick fashion to make you money by doing it fast. I remember how hard it was to learn stuff, and figure out how to do it right and quickly, and how hard it is to find the balance between quality and speed.