It is a magnetic reluctance pickup, excited by teeth in the flywheel.
( used to be called a 'reluctance head' pickup back in the day )
Cleaning the sensing end would have NO effect.
I think the problem is one of two things :
1. The engine vibration and heating/cooling cycles eventually causes a break in the internal coil wiring around the permanent magnet
or
2. The harness contacts just get dirty/corroded, unplugging and putting in a new sensor fixes that.