These units have redundant technology. Some of the contacts and blades are electrically the same. I have marked up your pic to illustrate the point. The two blades outlined in yellow are in contact with each other in the switch stack, making them electronically the same. The contact points outlined in red are obviously electrically the same as they are mounted to a single piece of "snakehead" shaped metal. So if either_ yellow blade contacts either_ red contact, the circuit is closed and passes current to generate a pulse signal.

SO, if one yellow blade/red contact pair has had their contact surface filed and burnished to a mirror finish it can carry enough juice for the circuit to function normally without the redundancy, and more importantly, without the pressure from the second blade as you can leave it mal-adjusted OPEN while the signals are passed by the other pair.

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