So you're saying it is giving you an extra ball, or is it just the "same player shoots again" light? If it's just the light, are the a-b-c lane lights working properly (do they come on after hitting the switch)?
If it is giving you the extra ball, check to see what your Extra Ball value is set to.
Could be that a previous owner had it set so low that it gives you an extra ball at very low points?