Moon dynamo deflectors

Lets say you drill a big hole right through the center of the Moon in the direction of its axis of rotation. Presuming there will be no atmosphere (almost vacuum) in the tube, and presuming that you wrap it with superconducting wire to fight eddy currents. If you let a permanent magnet free fall through it and oscilate due to gravity to create a potential energy storage of sorts (no rails) ---
What will be the forces which would cause the oscilating body to touch the tube walls in the end? Would rotation around Earth, and the Sun cause deflections? Or what would be the buggest influence?