Don't forget to check your lead (cord). They (can) often go "bad."
Does the input jack, make noise, when you wobble the cord, at the
input plug end.
Does the selector switch, crackle or cut-out, at times, when you
switch positions? Do your pots crackle or cut-out, too? Check for
loose connections, both at the input jack, or in the wiring, inside the
back cover. In the case of the input jack, it "might" be, just a matter
of bending (in) the prong, for a more secure fit? Does it do this, on
both pickups, or just the bridge or neck pickup, alone? Might be a
damaged winding..that only shorts, when in certain positions, and then
reconnects in others. Who knows? There are All kinds of possibilities.
Hope you can get it sorted out.
CB