likely was disconnected for the low coil broken-damaged and connected it'd start short stroke hammering on the main coil near EOS (buzz!). -without it in place risks burning the main coil if ball holding very long.

you can replace the coil if bad and put the switches back into the loop, or rewire main coil with EOS normally closed so when it opens it puts a resistor in series to the main coil, dropping voltage and current to the coil (as the resistor heats up of course!). resistor-switch "rewire hack" is what Sentinel-WonderWizard did for using a single coil for flippers, not the best method but effective. normally that EOS switch would bounce power from high to low coil when "on". either method will help to prevent burning a main coil, or its driver transistor.