If you replaced the coils with new ones, some are made with the diodes in a different order. You could have some wires crossed and the coil will still fire, but will overheat due to incorrect current. Triple check that it is wired correctly. Also, check to insure the tiny coil wire from the coil to the diode is not broken. My TAF thing flipper wire had broken and would do this, but only for a moment. Then it disengaged. If yours continuously fires rapidly without disengaging, then you probably wired it wrong.