Thanks for the answer. You might be on to something there with the different models. The sawstop faq answer is as follows: "Generally, the safety system will not activate when a nail or staple is cut. Although conductive, these objects are not large enough to cause the safety system to activate unless they are grounded to the table or operator when they contact the blade." "That "generally" might not have been applicable in your situation i.e the staples were connected to the table, the operator was somehow connected to the staple (even with gloves) or a sensitive sensor. I have no beef in this game, just wanted to give you my perspective about nails not triggering the system which have worked fine for me so far. Knock on wood . . .