My first actuator had magnets that alternated polarity N then S, N then S, etc. on the wheel. The sensor screwed into a white plastic mount so that it could be adjusted in or out to miss the rotating wheel. The sensor failed and I replaced it with a reed switch in a glass tube by soldering #14 copper wire to each end. The wire was stiff enough to hold it all in place. Worked fine but my count doubled which was an added benefit for Ku. I guess back then the magnet would either pull on the internal workings of the switch then push it out assuring full motion of the switch.