Quoted from MrBally:Actually, I'm not joking. Learned it at the Bally Service School in 1979. The ball and the track oxidize which causes quite a bit of electrical noise on the switch matrix.
Witinessed the problem dozens of times on machines that were over three years old on the route I worked for. It really worked for phantom flipper and thumper bumper activations.
This would make sense on why most Early SS bally's i've run into had the tilt ball removed.